এ বারের নোবেলজয়ী গবেষণার অন্তরালে এই বাঙালিও
নোবেল পুরস্কারের বাকি অর্ধেকটার সঙ্গে মৃণালের ১৯৫৩ সালের গবেষণার যোগাযোগ নিয়ে কোনও সাম্প্রতিক আলোচনা চোখে পড়েনি। তাই এই প্রবন্ধের অবতারণা।
ইনসেটে, প্রয়াত অধ্যাপক মৃণাল দাশগুপ্ত। গ্রাফিক: তিয়াসা দাস।
অর্ণব রায়চৌধুরী ও ঋতবান চট্টোপাধ্যায়
বেঙ্গালুরু ও কলকাতা
শেষ আপডেট: ১৯ নভেম্বর ২০২০ ০৯:০৯
স্যর আইজাক নিউটন একটি চিঠিতে লিখেছিলেন, তিনি যদি অন্যদের চেয়ে বেশি দূরে দেখতে পেয়ে থাকেন, তবে তার কারণটা হল, তিনি অতিমানবদের কাঁধের উপর ভর দিয়ে দাঁড়াতে পেরেছিলেন!
যে কোনও বিজ্ঞানীককেই এগোতে হয় তাঁর পূর্বসূরীদের কাজের ভিত্তিতে। এই বছর ব্ল্যাক হোল নিয়ে গবেষণার জন্য যাঁদের নোবেল পুরস্কার দেওয়া হল তাঁরাও এর ব্যাতিক্রম নন। নোবেল পুরস্কারের অর্ধেকটা এ বার যে জন্য রজার পেনরোজকে দেওয়া হয়েছে, তাঁর (ও সেই সঙ্গে স্টিফেন হকিং-এর) সেই কাজের অন্যতম পূর্বসূরী ছিলেন কলকাতার এক জন মাস্টারমশাই। তদানীন্তন প্রেসিডেন্সি কলেজের অধ্যাপক অমলকুমার রায়চৌধুরী। যাঁর জন্ম ১৯২৩ সালে। মৃত্যু ২০০৫-এ। কলকাতার সঙ্গে এ বারের এই অর্ধেক নোবেল পুরস্কারের যোগাযোগ নিয়ে সম্প্রতি বহু আলোচনা হয়েছে।
নোবেল পুরস্কারের বাকি অর্ধেকটা দেওয়া হয়েছে আন্দ্রিয়া ঘেজ এবং রাইনহার্ড গেনজেলকে। যাঁরা আমাদের মিল্কি ওয়ে গ্যালাক্সির কেন্দ্রে সূর্যের চেয়ে ৪০ লক্ষ গুণ ভারী একটি দানবাকৃতি ব্ল্যাক হোলের প্রথম সন্ধান দিয়েছিলেন। এই গবেষণারও এক জন পূর্বসূরী ছিলেন কলকাতারই আর এক মাস্টারমশাই। রাজাবাজার সায়েন্স কলেজে কলকাতা বিশ্ববিদ্যালয়ের রেডিয়োফিজিক্স ও ইলেকট্রনিক্স বিভাগের অধ্যাপক মৃণালকুমার দাশগুপ্ত। তাঁরও জন্ম হয়েছিল ১৯২৩-এ। মৃত্যু ২০০৫ সালে। এ বারের নোবেল পুরস্কারের এই বাকি অর্ধেকটার সঙ্গে মৃণালের ১৯৫৩ সালের গবেষণার যোগাযোগ নিয়ে কোনও সাম্প্রতিক আলোচনা আমাদের চোখে পড়েনি। তাই এই প্রবন্ধের অবতারণা।
অমল তাঁর বিখ্যাত কাজটি করেছিলেন কলকাতায় বসে। আর মৃণাল তাঁর কাজটা করেছিলেন ইংল্যাণ্ডের ম্যাঞ্চেস্টার বিশ্ববিদ্যালয়ে গবেষণার সময়। যদিও ম্যাঞ্চেস্টারের সাড়ে ৩ বছর ছাড়া তাঁর কর্মজীবনের পুরোটাই কেটেছে কলকাতার সায়েন্স কলেজে।
দুই লেখক ঋতবান চট্টোপাধ্যায় এবং অর্ণব রায়চৌধুরী (ডান দিকে)।
‘সিগনাস-এ’ গ্যালাক্সিতে রেডিয়ো তরঙ্গের যুগ্ম উৎস আবিষ্কার
১৯৫০-এ তরুণ মৃণাল একটি স্কলারশিপের জন্য নির্বাচিত হন। যাতে তাঁর সুযোগ হয় ম্যাঞ্চেস্টার বিশ্ববিদ্যালয়ে গিয়ে রেডিয়ো জ্যোতির্বিজ্ঞান নিয়ে গবেষণা করার।
সেই যুগে রেডিয়ো জ্যোতির্বিজ্ঞানে পৃথিবীর অন্যতম শ্রেষ্ঠ গবেষণাকেন্দ্র ছিল ম্যাঞ্চেস্টারের জড্রেল ব্যাঙ্কে। সেখানেই প্রবাদপ্রতিম বিজ্ঞানী হ্যানবেরি ব্রাউনের তত্ত্বাবধানে কাজ করার দুর্লভ সুযোগ মিলে যায় মৃণালের।
হ্যানবেরি ব্রাউনের আর এক ছাত্র ছিলেন রজার জেনিসন। মৃণালেরই সমবয়সী, ফলে দু’জনের মধ্যে গভীর বন্ধুত্বও হয়ে যায়। দুই বন্ধু মিলে একটি সম্পূর্ণ অপ্রত্যাশিত আবিষ্কার করে ফেলেন।
আরও পড়ুন- হকিং, পেনরোজ কি উদ্ভাসিত অমল আলোয়? কী বলছে ইতিহাস
রেডিয়ো জ্যোতির্বিজ্ঞানের তখন শৈশব। রেডিয়ো তরঙ্গের অনেকগুলো মহাজাগতিক উৎস চিহ্নিত হয়েছে। কিন্তু আকাশে সেগুলোর একেবারে নির্ভুল অবস্থান বা সঠিক আকৃতি নির্ণয় করা সম্ভব হয়নি।
জ্যোতির্বিজ্ঞানীদের জানা ছিল, সিগনাস-এ নামে একটি গ্যালাক্সি রেডিয়ো তরঙ্গের একটি উৎস। কিন্তু গ্যালাক্সিটার ভিতরে ঠিক কোন জায়গা থেকে রেডিয়ো তরঙ্গ বেরিয়ে আসছে তার হদিশ তাঁরা তখনও পাননি।
জড্রেল ব্যাঙ্কে মৃণাল দাশগুপ্ত (সৌজন্যে: জড্রেল ব্যাঙ্কের সংরক্ষণাগার)
আমরা জানি, যে টেলিস্কোপ আকারে যত বড় তার সাহায্যে কোনও নক্ষত্রের আকৃতি ও অভ্যন্তরীণ গঠন তত ভাল ভাবে দেখতে পাওয়া যায়।
৪০-এর দশকের শেষ ভাগে রেডিয়ো জ্যোতির্বিজ্ঞানীরা এমন একটা পদ্ধতি উদ্ভাবন করলেন যার মাধ্যমে একটি সুবিশাল রেডিয়ো টেলিস্কোপ ছাড়াও কোনও রেডিয়ো নক্ষত্রের আকৃতি নির্ণয় করা সম্ভব হল।
ধরা যাক, ১ কিলোমিটার ব্যবধানে রাখা দু’টো ছোট রেডিয়ো টেলিস্কোপ এক সঙ্গে একটা জ্যোতিষ্ককে পর্যবেক্ষণ করছে। এই দু’টো রেডিয়ো টেলিস্কোপের পর্যবেক্ষণের সমন্বয় ঘটিয়ে জ্যোতিষ্কটির এমন একটা ছবি বানানো গেল যা অনেকাংশেই ১ কিলোমিটার আয়তনের একটা রেডিয়ো টেলিস্কোপ দিয়ে তোলা ছবির প্রায় সমতুল্য।
এই পদ্ধতির নাম ‘রেডিয়ো ইন্টারফেরোমেট্রি’। যার অন্যতম পথিকৃৎ ছিলেন কেম্ব্রিজ বিশ্ববিদ্যালয়ের মার্টিন রাইল। যিনি নোবেল পান ১৯৭৪ সালে। জড্রেল ব্যাঙ্কে এই পদ্ধতিটিরই আরও উন্নতি ঘটালেন হ্যানবেরি ব্রাউন।
এই পদ্ধতিতে সিগনাস-এ পর্যবেক্ষণ করতে গিয়ে রজার জেনিসন এবং মৃণাল দাশগুপ্ত যে অত্যাশ্চর্য আবিষ্কারটা করে বসলেন তার জন্য সেই সময় কেউই তৈরি ছিলেন না। তাঁরা দেখতে পেলেন, রেডিয়ো তরঙ্গের উৎসটা গ্যালাক্সির ভিতরে নেই। বরং গ্যালাক্সির খানিকটা বাইরে তার দু’পাশে দু’টো রেডিয়ো তরঙ্গের উৎস রয়েছে।
রেডিয়ো তরঙ্গ ব্যবহার করে সিগনাস-এ’র যে ছবিটা তাঁরা তুললেন সেটা নীচে দেওয়া হল।
রজার-মৃণালের তোলা সিগনাস-এ’র ছবি। (গ্যালাক্সিটি রয়েছে দু’টি আয়তক্ষেত্রের মাঝামাঝি জায়গায়)।
যেন একটা ভুতুড়ে ব্যাপার। গ্যালাক্সির দু’পাশে প্রায় দেড় লক্ষ আলোকবর্ষ দূরে মহাকাশের দু’টো শূন্যস্থান থেকে রেডিয়ো তরঙ্গের সৃষ্টি হচ্ছে।
রজার এবং মৃণালের সেই গবেষণাপত্রটি ’৫৩-য় ‘নেচার’ পত্রিকায় প্রকাশিত হতেই আলোড়ন পড়ে যায় জ্যোতির্বিজ্ঞানের জগতে। কোনও বিজ্ঞানীই এই অদ্ভূত আবিষ্কারের কোনও সন্তোষজনক ব্যাখ্যা দিতে পারলেন না।
সেই সময়ের বেশির ভাগ বিজ্ঞানীই ব্ল্যাক হোলের অস্তিত্বে বিশ্বাস করতেন না। তাই রজার এবং মৃণালের আবিষ্কারের সঙ্গে যে ব্ল্যাক হোলের কোনও সম্পর্ক থাকতে পারে সেটা বুঝে উঠতেই জ্যোতির্বিজ্ঞানীদের আরও প্রায় ১৫ বছর লেগেছিল।
স্বাভাবিক ভাবেই রজার এবং মৃণালের গবেষণাপত্রের কোনও অংশেই ‘ব্ল্যাক হোল’ কথাটা এক বারও উল্লিখিত হয়নি।
সক্রিয় গ্যলাক্সির কেন্দ্রে ব্ল্যাক হোলের কাণ্ডকারখানা
মেঘের বর্ণনা দিতে গিয়ে কালিদাস লিখেছিলেন, মেঘ হল ‘ধূমজ্যোতিসলিলমরুতাংসন্নিপাতঃ’। যার অর্থ, ধূম, জ্যোতি, জল ও বায়ুর সমষ্টি মেঘ। তেমনই একটা গ্যালাক্সি হল নক্ষত্র, গ্যাস ও ধূলিকণার সমষ্টি।
জ্যোতির্বিজ্ঞানীদের হিসাব অনুযায়ী, আমাদের গ্যালাক্সিতে রয়েছে প্রায় ১০ হাজার কোটি নক্ষত্র। একটা গ্যালাক্সি থেকে বেরিয়ে আসা আলো অধিকাংশ ক্ষেত্রেই গ্যালাক্সিটার ভিতরে থাকা নক্ষত্রগুলোর সমন্বয়।
কিন্তু ১৯৪৩ সালে কার্ল সিফার্ট কতগুলো গ্যালাক্সিকে শনাক্ত করলেন, যেগুলোর কেন্দ্র খুব উজ্জ্বল।
সেই প্রথম বোঝা গেল, সব গ্যালাক্সির আলো শুধুই তাদের ভিতরে থাকা নক্ষত্রগুলির আলোর সমন্বয় নয়, গ্যালাক্সির কেন্দ্রেও অন্য কিছু একটা থাকতে পারে।
যে সব গ্যালাক্সির কেন্দ্রে এই রকম কিছু থাকে সেই সব গ্যালাক্সিকে জ্যোতির্বিজ্ঞানীরা ‘সক্রিয় গ্যালাক্সি’ নাম দিলেন।
সিফার্টের গবেষণার ভিত্তি ছিল দৃশ্যমান আলো। যে আলো আমরা খালি চোখে দেখতে পাই।
দ্বিতীয় বিশ্বযুদ্ধের পর যখন রেডিয়ো জ্যোতির্বিজ্ঞানের গবেষণা শুরু হল তখন বিজ্ঞানীরা মহাকাশ দেখার জন্য যেন একটা নতুন ‘চোখ’ পেয়ে গেলেন। সেই নতুন চোখের সহায়তায় সক্রিয় গ্যালাক্সি নিয়ে গবেষণাও দ্রুত গতিতে এগোতে লাগল।
প্রাথমিক ভাবে মনে হতে পারে, রজার এবং মৃণালের কাজের সঙ্গে সক্রিয় গ্যালাক্সির কোনও সম্পর্কই নেই।
কারণ, তাঁরা তো গ্যালাক্সির কেন্দ্রে কিছু দেখেননি। রেডিয়ো তরঙ্গের উৎসদু’টিকে তাঁরা দেখেছিলেন সিগনাস-এ গ্যালাক্সির বাইরে, খানিকটা দূরে। দেখেছিলেন, গ্যালাক্সির বাইরের শূন্যস্থান থেকে রেডিয়ো তরঙ্গ আসছে।
রেডিয়ো জ্যোতির্বিজ্ঞানের ইতিহাসে তাঁদের কাজ কেন সক্রিয় গ্যালাক্সি নিয়ে গবেষণার প্রথম উল্লেখযোগ্য পদক্ষেপ বলে মনে করা হয়, সেই আলোচনায় একটু পরে আসছি।
আরও পড়ুন- আমার বন্ধু রজার
৬০-এর দশকে জ্যোতির্বিজ্ঞানীরা রেডিয়ো তরঙ্গের কতগুলো উৎস আবিষ্কার করলেন। যেগুলোকে বলে, ‘কোয়েজার’।
বেশির ভাগ কোয়েজারই দৃশ্যমান আলোতেও দেখতে পাওয়া যায়। সেগুলিকে অনেকটা উজ্জ্বল নক্ষত্রের মতো দেখতে লাগে। কোয়েজারগুলো যে ঠিক কী বস্তু, তা নিয়ে জ্যোতির্বিজ্ঞানী মহলে সেই সময় কয়েক বছর ধরে তীব্র বাদানুবাদ চলেছিল।
মার্টেন স্মিড্ট এবং আরও কয়েক জন বিজ্ঞানীর গবেষণায় শেষ পর্যন্ত বোঝা যায়, কোয়েজারগুলো আসলে অত্যন্ত শক্তিশালী সক্রিয় গ্যালাক্সি। তাঁরা এও দেখালেন, কোয়েজারগুলোর কেন্দ্রগুলি আয়তনে আমাদের সৌরমণ্ডলের চেয়ে বড় নয়, কিন্তু এগুলোর ঔজ্জ্বল্য বহু ক্ষেত্রেই একটা গ্যালাক্সির সমান! অর্থাৎ, সূর্যের প্রায় ১০ হাজার কোটি গুণ।
স্বাভাবিক ভাবেই প্রশ্ন উঠল, একটা ছোট জায়গা থেকে এত বিপুল পরিমাণে শক্তির বিকিরণ কী ভাবে হতে পারে?
১৯১৫ সালে আইনস্টাইনের সাধারণ আপেক্ষিকতাবাদ প্রকাশিত হওয়ার সঙ্গে সঙ্গেই এই তত্ত্বের ভিত্তিতে ব্ল্যাক হোলের অস্তিত্ব অনুমিত হল। ব্ল্যাক হোলের মধ্যে মাধ্যাকর্ষণের বল এত বেশি যে আলোও সেই বল কাটিয়ে বেরিয়ে আসতে পারে না।
প্রায় অর্ধেক শতাব্দী ধরে অধিকাংশ জ্যোতির্বিজ্ঞানীই ব্ল্যাক হোলের অস্তিত্বে সন্দিহান ছিলেন। অনেকে আবার মনে করতেন, ব্ল্যাক হোল থাকলেও তার অস্তিত্ব কখনও আমাদের টেলিস্কোপে ধরা পড়বে না, কারণ ব্ল্যাক হোলের ভিতর থেকে তো আলো বেরিয়ে আসতে পারে না।
মস্কো ও কেম্ব্রিজের কয়েক জন তাত্ত্বিক জ্যোতির্পদার্থবিজ্ঞানী অবশেষে দেখালেন, যদি আমরা ধরে নিই যে একটা সক্রিয় গ্যালাক্সির কেন্দ্রে সূর্যের চেয়ে কয়েক লক্ষ থেকে কয়েক কোটি গুণ ভারি ব্ল্যাক হোল রয়েছে, তা হলে সমস্ত পর্যবেক্ষণ সুষ্ঠু ভাবে ব্যাখ্যা করা যায়।
আরও পড়ুন- দার্জিলিঙের সকালে রজার আমাকে সৃষ্টির রূপ বোঝাতে শুরু করলেন
অনেক গ্যালাক্সিরই কেন্দ্রের আশেপাশে গ্যাসের ভাণ্ডার যথেষ্টই মজুত রয়েছে। ব্ল্যাক হোলের প্রচণ্ড মাধ্যাকর্ষণের টানে এই গ্যাস ক্রমাগতই আকৃষ্ট হতে থাকে।
স্কুলের উঁচু ক্লাসের পদার্থবিজ্ঞানের পাঠ্যপুস্তকে একটা আলোচনা থাকে।সকোনও বস্তু মাধ্যাকর্ষণের টানে নিচের দিকে নামতে থাকলে তার স্থিতিশক্তি কমতে থাকে। ব্ল্যাক হোলের টানে যে গ্যাস আকৃষ্ট হয়, সেই গ্যাস ব্ল্যাক হোলের মধ্যে বিলীন হয়ে যাওয়ার আগেই তার হ্রাসপ্রাপ্ত স্থিতিশক্তির অনেকটা বিকিরণে পরিবর্তিত হয়ে যেতে পারে। এই ভাবেই ব্ল্যাক হোলের আশপাশে খুব অল্প জায়গার মধ্যে প্রচণ্ড বিকিরণ সৃষ্টি হয়ে নিঃসৃত হতে থাকে।
এটাই যে সক্রিয় গ্যালাক্সির উজ্জ্বল কেন্দ্রের সবচেয়ে সুসঙ্গত ব্যাখ্যা, তা আজ প্রায় সব জ্যোতির্বিজ্ঞানীই মেনে নিয়েছেন।
যুগ্ম রেডিও লোবে শক্তির সরবরাহ
রজার জেনিসন এবং মৃণাল দাশগুপ্তের আবিষ্কারের সঙ্গে গ্যালাক্সির কেন্দ্রের ব্ল্যাক হোলের কী সম্পর্ক সেই আলোচনায় আমরা এ বার আসব।
প্রথমেই বলে নিই, রজর-মৃণালের ’৫৩ সালের আবিষ্কারের কয়েক বছরের মধ্যেই রেডিও ইন্টারফেরোমেট্রি ব্যবহার করে জ্যোতির্বিজ্ঞানীরা আরও বেশ কয়েকটি মহাজাগতিক রেডিয়ো উৎসে একই রকম যুগ্ম গঠন দেখতে পেলেন।
বোঝা গেল, জ্যোতির্বিজ্ঞানের জগতে সিগনাস-এ একমেবাদ্বিতীয়ম নয়।
গ্যালাক্সির কেন্দ্র থেকে দূরে দু’পাশে যে দু’টো জায়গা থেকে রেডিয়ো তরঙ্গের সৃষ্টি হচ্ছে সেগুলোকে বলা হয় ‘রেডিয়ো লোব’।
বিজ্ঞানীরা হিসাব কষে দেখালেন, সিগনাস-এ’র রেডিয়ো লোবদু’টি থেকে মোট যতটা রেডিয়ো তরঙ্গের বিকিরণ হচ্ছে তার শক্তি প্রায় ১০ হাজার কোটি নক্ষত্র থেকে বেরিয়ে আসা আলোর শক্তির সমান।
মূল গ্যালাক্সি থেকে অত দূরে কী ভাবে এই পরিমাণ শক্তির বিকিরণ হচ্ছে, তার উত্তর খুঁজে বের করতে বিজ্ঞানীদের আরও কয়েক বছর সময় লেগে গেল।
আমরা অনেক সময়ই বলে থাকি, হাজারটা কথায় যার ব্যাখ্যা হয় না, তা শুধুমাত্র একটা ছবিতেই বুঝিয়ে দেওয়া যায়। এ বার আমরা একটা ছবি দেখাব যেটা দেখে পাঠকেরা নিজেরাই হয়তো আমাদের প্রশ্নটার উত্তর পেয়ে যাবেন।
ছবিটা হল, সাম্প্রতিক কালের পৃথিবীর একটা শ্রেষ্ঠ রেডিয়ো টেলিস্কোপ দিয়ে ইন্টারফেরোমেট্রি পদ্ধতি ব্যবহার করে তোলা সিগনাস-এ’র ছবি। রজার এবং মৃণালের ’৫৩ সালে তোলা ছবির সঙ্গে এই ছবিটার তুলনা করলেই বোঝা যায়, বিংশ শতাব্দীর দ্বিতীয়ার্ধে রেডিয়ো ইন্টারফেরোমেট্রি পদ্ধতিটার কী অভূতপূর্ব উন্নতি ঘটেছিল।
ইন্টারফেরোমেট্রি পদ্ধতি ব্যবহার করে তোলা সিগনাস-এ’র ছবি (ন্যাশনাল রেডিও অ্যাস্ট্রোনমি অবজারভেটরির সৌজন্যে)
কী ভাবে তৈরি হচ্ছে রেডিয়ো জেট?
সিগনাস-এ’র এই আধুনিক ছবিটায় স্পষ্টই দেখা যাচ্ছে, গ্যালাক্সির কেন্দ্র থেকে দু’পাশে দু’টো সরু গ্যাসের প্রবাহ। যেগুলোকে আমরা ‘রেডিও জেট’ বলি, তা বেরিয়ে এসেছে। এই জেটগুলো যেখানে শেষ হয়েছে সেখানেই লোবগুলোর সৃষ্টি।
অনুমান করতে অসুবিধা হয় না, গ্যালাক্সির কেন্দ্র থেকে জেটের মধ্যে দিয়ে যে শক্তি লোবগুলোতে এসে পৌঁছচ্ছে, সেই শক্তিই লোবগুলো থেকে রেডিয়ো তরঙ্গ হয়ে বিকিরিত হচ্ছে।
এ বার আমাদের সামনে যে প্রশ্নটা উঠে এল, তা হল; এই জেটগুলো কী ভাবে তৈরি হচ্ছে?
বেগেলম্যান, ব্ল্যাণ্ডফোর্ড ও রিসের প্রবন্ধে রজার-মৃণালের কাজের উল্লেখ
পৃথিবী যেমন নিজের অক্ষ ঘিরে ২৪ ঘন্টায় আবর্তিত হচ্ছে, ঠিক সেই ভাবেই গ্যালাক্সির কেন্দ্রের ব্ল্যাক হোলগুলোও নিজেদের অক্ষ ঘিরে আবর্তিত হয়ে চলেছে বলে জ্যোতির্বিজ্ঞানীরা মনে করেন।
এই রকম ঘূর্ণমান ব্ল্যাক হোলের উপর আশপাশ থেকে যে গ্যাস এসে পড়তে থাকে সেই গ্যাসের খানিকটা ব্ল্যাক হোলের মেরু অঞ্চল থেকে সবেগে নিক্ষিপ্ত হয়ে যেতে পারে।
এই ভাবেই যে রেডিয়ো জেটের সৃষ্টি হচ্ছে তা ১৯৭০-এর দশকে মার্টিন রিস, রজার ব্ল্যান্ডফোর্ড এবং তাঁদের সহকর্মীরা বিস্তারিত গণনা করে দেখালেন।
আরও পড়ুন- ‘আমার তত্ত্বের ফাঁকফোকর খুঁজছি, তোমরাও খুঁজে দেখ’, এখনও বলেন জিম পিবল্স
জেট ও লোব যে গ্যালাক্সির কেন্দ্রের ব্ল্যাক হোল থেকে উৎপন্ন হচ্ছে তা আজ জ্যোতির্বিজ্ঞানী মহলে স্বীকৃত।
রজার এবং মৃণালের আবিষ্কৃত সিগনাস-এ’র রেডিয়ো লোব যে ব্ল্যাক হোলের অস্তিত্বের স্পষ্ট ইঙ্গিত দেয়, তা আজ আর আমাদের বুঝতে অসুবিধা হয় না।
সিফার্টের যাত্রাপথে স্মরণীয় পদক্ষেপ রজার-মৃণালের
আমাদের গ্যালাক্সিকে যে হেতু সক্রিয় গ্যালাক্সি নয় বলেই জ্যোতির্বিজ্ঞানীরা মনে করেন, তাই আমাদের গ্যালাক্সির কেন্দ্রেও ব্ল্যাক হোল রয়েছে কি না তা নিয়ে বিজ্ঞানীদের মধ্যে খানিকটা সন্দেহ ছিল।
এই বছরের নোবেলজয়ী গেনজেল এবং ঘেজের গবেষণার ফলে ২০০৯-’১০ সাল নাগাদ বোঝা গেল, আমাদের গ্যালাক্সির কেন্দ্রেও ব্ল্যাক হোল রয়েছে। তাঁদের কাজ নিয়ে সম্প্রতি অনেক আলোচনা হয়েছে। তাই তাঁদের কাজের বিস্তৃত আলোচনায় যাব না।
সিফার্টের ’৪৩ সালের গবেষণাপত্রে যে যাত্রাপথের শুরু, সেই যাত্রাপথের অন্যতম পদক্ষেপ গেনজেল এবং ঘেজের আবিষ্কার।
গ্যালাক্সির কেন্দ্রে ব্ল্যাক হোল সন্ধানের এই যাত্রাপথে সিফার্টের কাজের পরে রজার এবং মৃণালের কাজই নিঃসন্দেহে দ্বিতীয় উল্লেখযোগ্য পদক্ষেপ।
মৃণালের জীবন নিয়ে কয়েকটা কথা লিখে আমাদের আলোচনার ইতি টানব। তাঁর জন্ম অবিভক্ত বাংলার বরিশালে, ১৯২৩ সালে। ঢাকা বিশ্ববিদ্যালয় থেকে এম এসসি শেষ করার সঙ্গে সঙ্গেই এল স্বাধীনতা ও দেশভাগ। তাঁর পরিবারের সকলেই সিদ্ধান্ত নিলেন কলকাতায় চলে আসার। সৌভাগ্যবশত, কলকাতা বিশ্ববিদ্যালয়ের অধ্যাপক শিশির কুমার মিত্রের সহকারীর কাজ পেয়ে গেলেন মৃণাল। শিশিরের উদ্যোগেই ম্যাঞ্চেস্টারে গিয়ে রেডিয়ো জ্যোতির্বিজ্ঞানের কাজ হাতেকলমে শেখার ব্যবস্থা হয়ে যায় মৃণালের। ম্যাঞ্চেস্টার থেকে ডক্টরেট ডিগ্রি নিয়ে দেশে ফিরে মৃণাল কলকাতা বিশ্ববিদ্যালয়ের সহকারী অধ্যাপকের পদ পান এবং এই বিশ্ববিদ্যালয়েই তাঁর কর্মজীবন অতিবাহিত করেন।
মৃণাল দাশগুপ্তই যে প্রথম আন্তর্জাতিক খ্যাতিসম্পন্ন ভারতীয় রেডিয়ো জ্যোতির্বিজ্ঞানী সেই কথাটা আমরা আজও শ্রদ্ধার সঙ্গে স্মরণ করি।
(অর্ণব রায়চৌধুরী বেঙ্গালুরুর ইন্ডিয়ান ইনস্টিটিউট অব সায়েন্সের অধ্যাপক। ঋতবান চট্টোপাধ্যায় কলকাতার প্রেসিডেন্সি বিশ্ববিদ্যালয়ের অধ্যাপক।)
গ্রাফিক: তিয়াসা দাস।
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Proprietary Rights
These Terms of Use govern your use of the websites, content and community services offered through www.anandabazar.com , other associated URLs ("Site") and all mobile applications ("Mobile Apps") and products and services offered by ABP Pvt Ltd.
"You" and / or "Your" and / or "User" shall include and mean the person who is accessing the aforesaid website www.anandabazar.com through any means available now and / or maybe available in the future.
You (the user) agree to access "the Site" and "Mobile Apps", subject to the terms and conditions of use as set out here.
ABP Pvt.Ltd., the owner and / or publisher of www.anandabazar.com may add to or change or update these Terms of Use, from time to time entirely at the its own discretion. You are responsible for checking these Terms of Use periodically to remain in compliance with these terms. Your use of a Site after any amendment to the Terms of Use shall constitute your acceptance of these terms and you also agree to be bound by any such changes/revisions. By using this site you hereby represent and warrant that you are hereby bound by these Terms of Use and it's any amendments thereof and further represent that you are more than 18 (eighteen) years of age and otherwise competent to bound yourself into a valid contract as per the Laws of India. In the event you are below the age of 18 (eighteen) years then it shall be deemed that you are using this site under the guidance and supervision of your natural parent and / or guardian.
Governing Law and Meanings:-
These Terms of Use are being governed by the Laws of India and meaning of words used herein in connection with the use of the said website shall bear the meaning as may be envisaged and interpreted by the Information Technology Act, 2000 and any of its Amendment Acts.
Changes
ABP Pvt. LTD. reserves the right to suspend / cancel, or discontinue any or all channels, products or service at any time without notice , make modifications and alterations in any or all of the content, products and services contained on the site without prior notice. Such changes will be posted to "www.anandabazar.com" for your reference and convenience so as to enable you to understand your responsibility as a user.
Charges
ABP Pvt. LTD. reserves the right to charge subscription and / or membership fees from a user in respect of any product, service or any other aspect of this Site. Such charge of fees may be without any prior intimation at the sole discretion of ABP Pvt. Ltd.
Copyright and Trademarks
Unless otherwise stated, copyright and all intellectual property rights in all material presented on the site (including but not limited to text, audio, video or graphical images), trademarks and logos appearing on this site are the property of ABP Pvt. Ltd. Limited, its parent, affiliates and associates and are protected under applicable Indian laws. You agree not to use any framing techniques to enclose any trademark or logo or other proprietary information of ABP PVT. LTD.; or remove, conceal or obliterate any copyright or other proprietary notice or any credit-line or date-line on other mark or source identifier included on the Site / Service, including without limitation, the size, color, location or style of all proprietary marks. Any infringement shall be vigorously defended and pursued to the fullest extent permitted by law.
Limited Permission to Copy
ABP Pvt. Ltd. grants you permission to only access and make personal use of the Site and You agree not to, directly or indirectly download or modify / alter / change / amend / vary / transform / revise / translate / copy / publish / distribute or otherwise disseminate any content on ABP Pvt.Ltd.'s Site / Service, or any portion of it; or delete or fail to display any promotional taglines included in the Site / Service either directly or indirectly, except with the express consent of ABP Pvt. Ltd.
However, you may print or download extracts from these pages for your personal / individual, non-commercial use only. You must not retain any copies of these pages saved to disk or to any other storage medium except for the purposes of using the same for subsequent viewing purposes or to print extracts for personal / individual use.
ABP Pvt. Ltd. forbids you from any attempts to resell or put to commercial use any part of the Site; any collection and use of any product listings, descriptions, or prices; any derivative use of the Site or its contents; any downloading or copying of account information for the benefit of any other merchant; any renting, leasing, or otherwise transferring rights to the Site / Service; displaying the name, logo, trademark or other identifier of another person in such a manner as to give the viewer the impression that such other person is a publisher or distributor of the Service on the Site, or any data gathering or extraction tools; or any use of meta tags. You may not (whether directly or through the use of any software program) create a database in electronic or structured manual form by regularly or systematically downloading and storing all or any part of the pages from this site.
No part of the Site may be reproduced or transmitted to or stored in any other web site, nor may any of its pages or part thereof be disseminated in any electronic or non-electronic form, nor included in any public or private electronic retrieval system or service without prior written permission.
Individual Registration, Access and Exchange of Information
For certain services such as email, personal web pages, contests and shopping, registration by the visitor is required. To register for these services you have to open an account by completing the registration process (i.e. by providing us with current, complete and accurate information as prompted by the applicable registration form). You also will choose a password and a user name. You are entirely responsible for maintaining the confidentiality of your password and account and shall be responsible for the security of the connection and / or network that you are using. By registering, you agree to the following terms in addition to any other specific terms which shall be posted at an appropriate location of the Site. Each registration is for a single individual user only.
To access these services, you will be asked to enter your individual User Name and Password, as chosen by you during your registration. Therefore, we do not permit any of the following:-
• Any other person sharing your account and Password;
• Any part of the Site being cached in proxy servers and accessed by individuals who have not registered with www.anandabazar.com as users of the Site; or
• Access through a single account and Password being made available to multiple users on a network.
If ABP Pvt. Ltd. reasonably believes that an account and Password is being used / misused in any manner, ABP Pvt. Ltd. shall reserve the right to cancel access rights immediately without notice, and block access to all users from that IP address.
Furthermore, you are entirely responsible for any and all activities that occur under your account. You agree to notify ABP Pvt. Ltd. immediately of any unauthorized use of your account or any other breach of security. ABP Pvt. Ltd. will not be liable for any loss that you may incur as a result of someone else using your password or account. However, you could be held liable for losses incurred by ABP PVT. LTD. or another party due to someone else using your account or password.
No unlawful or prohibited use
As a condition of your use of the Services, you will not use the Services for any purpose that is unlawful or prohibited by these terms, conditions, and notices. You may not use the Services in any manner that could damage, disable, overburden, or impair any ABP PVT. LTD.'s server, or the network(s) connected to any ABP PVT. LTD.'s server, or interfere with any other party's use and enjoyment of any Services. You may not attempt to gain unauthorized access to any Services, other accounts, computer systems or to any of the Services, through hacking, password mining or any other means. You may not obtain or attempt to obtain any materials or information through any means not intentionally made available through the Services.
Material Posted/transmitted at www.anandabazar.com by the user and /or any third party:
All information, data, text, software, music, sound, photographs, graphics, video, messages or other materials ("Content"), whether publicly or privately transmitted / posted, is the sole responsibility of the person from where such content is originated (the Originator). By Posting any material which contain images, photographs, pictures or that are otherwise graphical in whole or in part ("Images"), you warrant and represent that (a) you are the copyright owner of such Images, or that the copyright owner of such Images has granted you permission to use such Images or any content and/or images contained in such Images consistent with the manner and purpose of your use and as otherwise permitted by these Terms of Use and the Services, (b) you have the rights necessary to grant the licenses and sublicenses described in these Terms of Use, and (c) that each person depicted in such Images, if any, has provided consent to the use of the Images as set forth in these Terms of Use, including, by way of limitation, the distribution, public display and reproduction of such Images.
You represent that you have valid rights and title in any and all Content/Images that you submit on the Site, that you have not infringed on any IPR belonging to any party and further that you will indemnify ABP PVT. LTD or its affiliates for all claims arising out of any content that you post on the Site.
ABP PVT. LTD. accepts no responsibility for the said Content / Images. However, you understand that all Content / Images posted by you becomes the property of ABP PVT. LTD. and you agree to grant/assign to ABP PVT. LTD. and its affiliates, a non-exclusive, royalty free, perpetual, irrevocable and sub-licenseable right to use, reproduce, modify, adapt, publish, translate, create derivative works from, distribute, perform and display such Content / Images (in whole or part) worldwide and/or to incorporate it in other works in any form, media, or technology now known or later developed throughout the world".
Limitations of Liabilities
Any transactions relating to sale/purchase of goods or services not directly offered by ABP PVT. LTD. are to be settled inter-se between the parties to such transaction and all warranties express or implied of any kind, regarding any matter pertaining thereto, including without limitation the implied warranties of merchantability, fitness for a particular purpose, and non-infringement are disclaimed by ABP PVT. LTD.
ABP PVT. LTD. merely endeavors to provide a platform where you and other party may interact, exchange information or carry out sale/purchase transactions on such terms and in the manner mutually agreed between you and the other party. ABP PVT. LTD. does not have any involvement in the actual transactions between the buyers and sellers in any way. It is only you, who is entirely responsible for all the activities, arising out of the transactions of sale/purchase of goods or services offered by any other party and not ABP PVT. LTD. ABP PVT. LTD. will not be liable for any loss that you may incur, while selling or purchasing goods /services of the third party.
Under No circumstances will ABP PVT. LTD. be held responsible or liable, in any way, for any content which in Legal opinion is derogatory, threatening, defamatory, obscene or offensive or offends public sensibilities or morals and shall also not assume liability for any errors or omissions in any content, or for any loss or damage of any kind incurred as a result of the use of any content posted or uploaded on the Site, or any infringement of another's rights, including intellectual property rights. You specifically agree that ABP PVT. LTD. is not responsible for any content sent using and/or included in ABP PVT. LTD.'s site/service by any third party.
Individual Registration and Access
Certain Services offered by the Company through www.anandazar.com platform, such as email, personal web pages, contests and shopping, require prior registration by the User. To gain access to such Services, You will be required to create an account by completing the registration process. As part of such registration process, You will be required to provide Us with current, complete and accurate information pertaining to such details as prompted by the applicable registration form. You will also be required to choose a unique password and a user name, which shall be entered by You every time You wish to gain access to the said Services. You shall not be entitled to gain, and shall not facilitate, access to www.anandabazar.com platform through a single account and password, by multiple users on a network. You agree and understand that We do not permit any part of www.anandabazar.com platform being cached in proxy servers. You are entirely responsible for maintaining the confidentiality of Your password and account.
If the Company reasonably believes that Your account and/or Password is being/ has been misused in any manner, the Company shall reserve the right to cancel access rights immediately without notice, and block access to all users from that IP address.
You shall not share your account information and password with others or use anyone else’s account. You are entirely responsible for any and all activities that occur under Your account. You agree to notify us immediately of any unauthorized use of your account or any other breach of security. In such an event, we shall do our best to help you recover your account; however, we cannot guarantee that your account will be restored or the content contained therein will be recovered. We will not be liable for any loss that you may incur as a result of unauthorized use of your password or account. However, you could be held liable for losses incurred by the Company or another party due to someone else using your account or password.
International Users
You agree and understand that the Services are controlled and operated by the Company from its offices in India. You agree that: (i) the Services shall be deemed solely based in India; and (ii) the use of the Services do not give rise to personal jurisdiction over the Company, either specific or general, in jurisdictions other than India. You agree that the laws of India, excluding India’s choice of law rules, will apply to this Terms of Use and Privacy Policy and all other policies and guidelines provided by the Company and to the provision of Services by the Company.
Access to www.anandabazar.com platform and/ or the Services from jurisdictions other than India where the same are illegal is prohibited. The Company reserves the right to block access to www.anandabazar.com platform and/ or the Services by such prohibited access by international users. If you access www.anandabazar.com platform and/ or the Services from a location outside India, you waive any right available under laws of jurisdictions outside of India.
Individual Registration and Access
Certain Services offered by the Company through www.anandazar.com platform, such as email, personal web pages, contests and shopping, require prior registration by the User. To gain access to such Services, You will be required to create an account by completing the registration process. As part of such registration process, You will be required to provide Us with current, complete and accurate information pertaining to such details as prompted by the applicable registration form. You will also be required to choose a unique password and a user name, which shall be entered by You every time You wish to gain access to the said Services. You shall not be entitled to gain, and shall not facilitate, access to www.anandabazar.com platform through a single account and password, by multiple users on a network. You agree and understand that We do not permit any part of www.anandabazar.com platform being cached in proxy servers. You are entirely responsible for maintaining the confidentiality of Your password and account.
If the Company reasonably believes that Your account and/or Password is being/ has been misused in any manner, the Company shall reserve the right to cancel access rights immediately without notice, and block access to all users from that IP address.
You shall not share your account information and password with others or use anyone else’s account. You are entirely responsible for any and all activities that occur under Your account. You agree to notify us immediately of any unauthorized use of your account or any other breach of security. In such an event, we shall do our best to help you recover your account; however, we cannot guarantee that your account will be restored or the content contained therein will be recovered. We will not be liable for any loss that you may incur as a result of unauthorized use of your password or account. However, you could be held liable for losses incurred by the Company or another party due to someone else using your account or password.
International Users
You agree and understand that the Services are controlled and operated by the Company from its offices in India. You agree that: (i) the Services shall be deemed solely based in India; and (ii) the use of the Services do not give rise to personal jurisdiction over the Company, either specific or general, in jurisdictions other than India. You agree that the laws of India, excluding India’s choice of law rules, will apply to this Terms of Use and Privacy Policy and all other policies and guidelines provided by the Company and to the provision of Services by the Company.
Access to www.anandabazar.com platform and/ or the Services from jurisdictions other than India where the same are illegal is prohibited. The Company reserves the right to block access to www.anandabazar.com platform and/ or the Services by such prohibited access by international users. If you access www.anandabazar.com platform and/ or the Services from a location outside India, you waive any right available under laws of jurisdictions outside of India.
Termination of Account
ABP PVT. LTD. reserves its right to refuse service, restrict, suspend, terminate your account; (Terminate this Agreement; Terminate or suspend your access to the ABP Web Sites; Refuse, move or remove for any reason any Content / Image that you submit on or through the Services; Refuse, move, or remove any Content / Image that is available on or through the Services; Deactivate or delete your accounts and all related information and files in your account; Establish general practices and limits concerning use of the Services) at any time and, remove or edit contents or cancel orders (entered by you) in its sole discretion with or without cause, and with or without any prior notice for any violation of the Terms of Use. Upon such termination or suspension, your right to use the ABP PVT. Ltd.'s Web Sites will immediately cease.
You can terminate Your account at any time by writing to service@anandabazar.com but your information may remain stored in archive on Our servers even after the deletion or the termination of Your account.
User Conduct and Obligations
You hereby agree and assure ABP PVT. Ltd. that the Site/Services shall be used for lawful purposes only and that you will not violate laws, regulations, ordinances or other such requirements of any applicable Central, State or local government or any other international laws. You further concur that you will not, through Site/Service:
• post, distribute, or otherwise make available or transmit any software or other computer files that contain a virus trojan horses, time bombs, bots, botnets, malicious content, content theft, data manipulation, threats or any other harmful programs or elements or component;
• delete from the Site any legal notices, disclaimers, or proprietary notices such as copyright or trademark symbols, or modify any logos that you do not own or have express permission to modify;
• not use the Site / Service in any manner that could damage, disable, overburden, or impair and not to undertake any action which is harmful or potentially harmful to any ABP PVT. LTD.'s server, or the network(s), computer systems / resource connected to any ABP PVT. LTD. server, or interfere with any other party's use and enjoyment of the Site/Service;
• obtain or attempt to obtain any materials or information through any means not intentionally made available through the Site/Service;
• engage in any activity that causes / may harm minors; or
• perform any activity which is likely to cause such harm;
• impersonate any person or entity, including, but not limited to, ABP PVT. LTD.'s official, forum leader, guide or host, or falsely state or otherwise misrepresent your affiliation with a person or entity;
• take any action which encourages or consists of any threat of harm of any kind to any person or property;
• carry out any "denial of service" (DoS, DDoS) or any other harmful attacks on application or internet service or;
• make any inappropriate, illegal or otherwise prohibited communication to any Newsgroup, Mailing List, Chat Facility, or other Internet Forum;
• use the Site/Service for illegal purposes;
• disrupt, place unreasonable burdens or excessive loads on, interfere with or attempt to make or attempt any unauthorized access to any ABP PVT. LTD website or the website of any ABP PVT.LTD.'s customer;
• transmit through the Site, any unlawful, harassing, libelous, abusive, threatening, harmful, vulgar, obscene, libelous, hateful, or racially, ethnically or otherwise objectionable material of any kind or nature. This includes text, graphics, video, programs or audio, etc;
• collect or attempt to collect personally identifiable information of any person or entity without their express written consent and you shall maintain records of any such written consent throughout the terms of this agreement and for a period of 2 years thereafter;
• engage in antisocial, disruptive, or destructive acts, including "flaming," "spamming," "flooding," "trolling," and "griefing" as those terms are commonly understood and used on the Internet
• forge headers or otherwise manipulate identifiers in order to disguise the origin of any content transmitted through the Site.
• upload, post, email, transmit or otherwise make available any unsolicited or unauthorised advertising, promotional materials, "junk mail," "spam," "chain letters," "pyramid schemes," duplicative messages or any other form of solicitation.
• encumber or suffer to exist any lien or security interest on the subject matter of this Agreement; or
• make any representation or warranty on behalf of ABP PVT. LTD.
You agree not to post, distribute, transmit or otherwise make available any data, text, message, computer file, or other material that infringes and/or violates any right of a third party or any domestic or international law, rule, or regulation, including but not limited to:
• infringement of any copyright, trademark, patent, trade secret, or other proprietary rights of any third party, including, but not limited to, the unauthorized copying of copyrighted material, the digitization and distribution of photographs from magazines, books, or other copyrighted sources, and the unauthorized transmittal of copyrighted software;
• Right of privacy (specifically, you must not distribute another person's personal information of any kind without their express permission) or publicity;
• Any confidentiality obligation.
Unless otherwise permitted, you will: (i) display the Service on your Site in the exact form received by you, and not modify or edit any of the foregoing without ABP PVT. Ltd.'s prior written consent; (ii) ensure that the fundamental meaning of the Service is not changed or distorted; (iii) comply with all applicable laws and all limitations and restrictions (if any) placed by ABP PVT. Ltd. on the use, display or distribution of any Service and (iv) not archive any of the Service for access by users at any future date after the Service has been removed from your Web site. You acknowledge that the service must link and redirect to the appropriate ABP PVT. Ltd.'s Web page when a user clicks on the Service (e.g. a headline). You shall not display the Service in such a manner that does not allow for successful linking and redirection to, and delivery of, ABP PVT. Ltd.'s Web page, nor may you frame any ABP PVT. Ltd.'s Web page.
No Controlling Spam Policy or Unsolicited E-mails
You will not use any communication tool or other means available on the Site to transmit, directly or indirectly, any unsolicited bulk communications (including emails and instant messages). You may not harvest information about users of ABP PVT. LTD. for the purpose of sending or to facilitate the sending of unsolicited bulk communications. We may terminate your access or use of the Site immediately, with or without any notice, and take any other legal action if you, or anyone using your access details to the Site, violates these terms. We may adopt any technical remedy (including any filtering technology or other measures) to prevent unsolicited bulk communications from entering, or remaining within our computer or communication networks. Such filtering technology or other measures may block, either temporarily or permanently, some e-mail sent to you through the ABP PVT. Ltd.'s Web Sites.
Disclaimer of Warranties and Liability
limitation, the implied warranties of merchantability, fitness for a particular purpose, workmanlike effort, title and non-infringement are disclaimed and excluded.
ABP PVT. Ltd. and its parent, affiliates and associates shall not be liable, at any time for any, direct, indirect, punitive, incidental, special, consequential, damages (including, without limitation, damages for loss of business projects, damage to your computer system or damages for loss of profits, damages for loss of use, data or profits, arising out of or in any way connected with the use or performance of the ABP PVT. Ltd.'s sites/services, with the delay or inability to use the ABP PVT. Ltd.'s sites/services or related services, the provision of or failure to provide services, or for any information, software, products, services and related graphics obtained through the ABP PVT. LTD. sites/services, or otherwise arising out of the use of the ABP PVT. LTD. sites/services) arising in contract, tort or otherwise from the use of or inability to use the Site, or any of its contents, or from any act or omissions a result of using the Site or any such contents or for any failure of performance, error, omission, interruption, deletion, defect, delay in operation or transmission, computer virus, communications line failure, theft or destruction or unauthorised access to, alteration of, or use of information contained on the site. No representations, warranties or guarantees whatsoever are made by ABP PVT. LTD. as to the (a) accuracy, adequacy, reliability, completeness, suitability or applicability of the information to a particular situation; (b) that the service will be uninterrupted, timely, secure, or error-free; (c) the quality of any products, services, content, information, or other material purchased or obtained from the website will meet your expectations or requirements; or (d) any errors in the website will be corrected.
Links to Other Sites
All the contents of this Site are only for general information or use. They do not constitute advice and should not be relied upon in making (or refraining from making) any decision. Any specific advice or replies to queries in any part of the Site is/are the personal opinion of such experts/consultants/persons and are not subscribed to by this Site. The information from or through this site is provided on "AS IS" basis, and all warranties and conditions, expressed or implied of any kind, regarding any matter pertaining to any goods, service or channel, including without Certain links on the Site lead to resources located on servers maintained by third parties, these sites of third party(s) may contain ABP PVT. LTD.'s-logo, please understand that it is independent from ABP PVT. LTD., over whom ABP PVT. LTD. has no control or connection, business or otherwise as these sites are external to ABP PVT. LTD. You agree and understand that by visiting such sites you are beyond the ABP PVT. LTD.'s website. ABP PVT. LTD., therefore neither endorses nor offers any judgement or warranty and accepts no responsibility or liability for the authenticity, availability, suitability, reliability, accuracy of the information, software, products, services and related graphics contained, of any of the goods/services/or for any damage, loss or harm, direct or consequential or any violation of local or international laws that may be incurred by your visit and/or transaction/s on these site(s), as the same is provided on "as is" without warranty of any kind. ABP PVT. LTD. gives no warranty and makes no representation whether expressed or implied, that the information contained in this site is error free. ABP PVT. LTD. shall not be responsible nor liable for any consequential damages arising on account of your relying on the contents of the advertisement. Before relying on the material, users should independently verify its relevance for their purposes, and should obtain any appropriate professional advice.
Material Submitted by Users
Certain elements of the Site will contain material submitted by users. ABP PVT. LTD. accepts no responsibility for the content, accuracy, conformity to applicable laws of such material. You will indemnify and hold harmless ABP PVT. LTD. against all third party claims, demands and actions brought against ABP PVT. LTD. which arises from or relates to the material submitted by you.
Advertising Material
Part of the Site contains advertising information or promotion material or other material submitted to ABP PVT. LTD. by third parties. Responsibility for ensuring that material submitted for inclusion on Site complies with applicable International and National law is exclusively on the party providing the information/material. Your correspondence or business dealings with, or participation in promotions of, advertisers other than ABP PVT. LTD. found on or through the Website, including payment and delivery of related goods or services, and any other terms, conditions, warranties or representations associated with such dealings, are solely between You and such advertiser. ABP PVT. LTD. will not be responsible or liable for any claim, error, omission, inaccuracy in advertising material or any loss or damage of any sort incurred as the result of any such dealings or as the result of the presence of such non-ABP PVT. LTD. advertisers on the Website. ABP PVT. LTD. reserves the right to omit, suspend or change the position of any advertising material submitted for insertion. Acceptance of advertisements on the Site will be subject to these terms and conditions.
Data Protection
ABP PVT. LTD. may send information and offer products and services to you from time to time. For further details relating to our policy relating to such offer please refer to our privacy statement. Notwithstanding the foregoing, ABP PVT. LTD. reserves the right to disclose any information in response to / that it is required to be shared, disclosed or make made available to any governmental, administrative, regulatory or judicial authority under any law or regulation applicable to ABP PVT. LTD.
Further, ABP PVT. LTD. can (and you authorize ABP PVT. LTD. to) disclose your name, street address, city, state, zip code, country, phone number, email, and company name to Intellectual Property rights owners, as we in our sole discretion believe necessary or appropriate in connection with an investigation of fraud, intellectual property infringement, piracy, or other unlawful activity.
Relationship
None of the provisions of the User Agreement shall be deemed to constitute a partnership or agency between you and ABP PVT. LTD. and you shall have no authority to bind ABP PVT. LTD. in any manner, whatsoever.
Force Majeure
ABP PVT. LTD. shall have no liability to you for any interruption or delay, to access the Site irrespective of the cause.
Indian Law
The Agreement shall be governed by the Laws of India. The Courts of law at Kolkata, West Bengal, India shall have exclusive jurisdiction over any disputes arising under this agreement.
Entire Agreement
These Terms of Service constitute the entire agreement between the parties with respect to the subject matter hereof and supersedes and replaces all prior or contemporaneous understandings or agreements, written or oral, regarding such subject matter.
Right to remove inappropriate messages
We reserve the right to remove any messages we deem to be inappropriate, i.e, racist, sexist or threatening. Messages using inappropriate language will also be removed. We do not wish to be censors, but our forums must remain civilized and respect the rights of others.
Limited time to bring your claim
You and ABP PVT. LTD. agree that any cause of action arising out of or related to the ABP PVT. LTD.'s web sites, only, must commence within one (1) year after the cause of action accrues otherwise, such cause of action will be permanently barred.
Acceptance of Terms & Conditions
By using ABP PVT. LTD.'s sites and services, you signify your acceptance of this Terms & Conditions. If you do not agree or are not comfortable with any term described in this Term & Conditions, your only remedy is to discontinue use of ABP PVT. LTD. sites. We reserve the right, to modify this Terns & Conditions at any time.
General Terms
Rights and obligations under the Terms which by their nature should survive will remain in full effect after termination or expiration of the Terms.
Any express waiver or failure to exercise promptly any right under the Terms will not create a continuing waiver or any expectation of non-enforcement.
If any provision of the Terms is held invalid by any law or regulation of any government, or by any court or arbitrator, the parties agree that such provision will be replaced with a new provision that accomplishes the original business purpose, and the other provisions of the Terms will remain in full force and effect.
Notice of Copyright Infringement
ABP PVT. LTD. is not liable for any infringement of copyright arising out of materials posted on or transmitted through the site, or items advertised on the site, by end users or any other third parties. Our policy is to comply with all Intellectual Property Laws and to act expeditiously upon receiving any notice of claimed infringement. If you believe that your work has been reproduced on this website in a manner that constitutes copyright infringement, please provide a notice of copyright infringement containing all of the following information:
(a)A physical or electronic signature of a person authorized to act on behalf of the copyright owner for the purposes of the complaint.
(b)Identification of the copyrighted work claimed to have been infringed.
(c)Identification of the material on our website that is claimed to be infringing or to be the subject of infringing activity.
(d)The address, telephone number or e-mail address of the complaining party.
(e)A statement that the complaining party has a good-faith belief that use of the material in the manner complained of is not authorized by the copyright owner, its agent or the law.
(f)A statement, under penalty of perjury, that the information in the notice of copyright infringement is accurate, and that the complaining party is authorized to act on behalf of the owner of the right that is allegedly infringed.
All notices of copyright infringement should be sent to:
ABP Pvt. Ltd.
www.anandabazar.com
ABP Pvt. Ltd. 6, Prafulla Sarkar St. Kolkata-700001, West Bengal, India
+913322345374
WHAT INFORMATION DO WE GATHER ABOUT YOU?
The information gathered when you interact with ABP falls into two categories: 1) Personal information, which includes personal information you supply when you subscribe, order, complete a survey, register for one of our sites, enter a contest or provide your email address and 2) Non-personal information collected through technology, which includes tracking information collected by us as well as third parties.
Personal Information That You Give Us or Ask a Third Party to Share with Us
Registration Information
Registration for ABP may require that you supply certain personal information, including a unique email address and demographic information (ZIP code, age, sex, household income, job industry and job title) to register.
You may register or enhance your profile by linking your Facebook or Google accounts on ABP. By doing this, you are asking them to send us certain information from those social media accounts, and you are authorizing us to collect, store, and use what they send us in accordance with this Privacy Policy.
Social media registration features may collect your IP address, the page you are visiting on our site, and may set a cookie to enable the feature to function properly. Social media features and widgets are either hosted by a third party or hosted directly on our website. You can disassociate your ABP registration from third-party accounts any time.
Kindly note that ABP shall not responsible for any information collected by the third party from you.
User Generated Content and Public Activities (Including Comments and Reader Reviews)
We offer you opportunities to engage in public activities on ABP.com and other ABP Services. "Public activities" are any actions you take on ABP that are designed to be visible to other users, including comments, recommendations, reader reviews, ratings or any other items that you submit. Any information you disclose in your public activities, along with your screen name or ID, or any image or photo, becomes public and may be used by ABP for online and offline promotional or commercial uses in any and all media. If you choose to engage in public activities, you should be aware that any personal information you submit can be read, collected and used by other users of these areas. We are not responsible for the personal information you choose to submit in the course of your public activities and we have no responsibility to publish, take down, remove or edit any of your public activities or submissions. For more information, see Terms of Service.
Public activities may be included in our RSS feeds, APIs and other distribution formats. As a result, your public activities may appear on other websites, blogs, or feeds. Keep in mind that we are not responsible for any personal information you choose to make public via your public activities, and you agree that such sharing will be deemed to have been done by you, not ABP including but not limited to sharing of information in your connected social media accounts.
When you share or recommend links to content on a third-party platform (such as Facebook, Google+ and Twitter), that action and any information you share will be covered by their privacy policy.
Contests, Sweepstakes and Special Offers
ABP collects personal information from you when you participate in sweepstakes, contests or special offers. If this information is also being collected by a third party other than ABP, we will notify you at the same time. If you do not want any personal information shared, you should not participate in the sweepstakes, contest or special offer.
Reader Surveys, Reader Panels and Market Research
ABP may collect personal information from you in connection with voluntary surveys conducted via ABP. Data may be collected through ABP, on the phone or through the mail. The information you provide may be shared, but only in the aggregate, with advertisers and partners unless we notify you otherwise at the time of collection.
Members of our Reader Panels agree to participate in surveys, polls or discussions about their readership of ABP, their household/personal characteristics and their purchase behavior.
Conferences and Live Events
We often receive information about attendees to our live events from sign-in and registration lists. We may share this information with event or promotion sponsors, in which case we will notify you when we collect the information.
Non-Personal Information Collected Using Technology
Information Collected by Us Using Technology
We use various internet technologies to manage ABP and track use of the Services. Non-personal information that we collect using these technologies may be combined with other information about you.
Device Information. We may collect non-personal information about the computer, mobile device or other device you use to access ABP, such as IP address, geolocation information, unique device identifiers, browser type, browser language and other transactional information.
Cookies, Beacons, Local Storage and Other Similar Technologies. We use "cookies," web beacons, tags and scripts, and other similar technologies including local storage objects such as HTML5. These technologies allow us to manage access to and use of the Services, recognize you and provide personalization, and help us understand how people use ABP. You will not be able to access certain areas of our websites, including ABP, if your computer does not accept cookies from us. We do not respond to browser-based "do not track" signals. For more detailed information about our use of cookies and local storage, and how to manage them, see Frequently Asked Questions About Cookies.
We may transmit non-personally identifiable website usage information to third parties in order to show you advertising for ABP when you visit other sites. For more information about our third-party ad server, or to learn your choices about not having this non-personal information used to target ads to you, please click here.
Local Storage Objects
We may use Local Storage Objects (LSOs) such as HTML5 to store content information and preferences. Third parties with whom we partner to provide certain features on our site or to display advertising based upon your web browsing activity use LSOs such as HTML 5 or Flash to collect and store information.
Various browsers may offer their own management tools for removing HTML5 LSOs. To manage Flash LSOs please click here:
http://www.macromedia.com/support/
documentation/en/flashplayer/
help/settings_manager07.html
Analytics, Log Files and Reading History
As is true of most websites, we gather certain information automatically and store it in log files. This information may include internet protocol (IP) addresses (the region or general location where your computer or device is accessing the internet), browser type, operating system and other usage information about the use of ABP, including a history of the pages you view.
We may combine this automatically collected log information with other information we collect about you. We do this to improve services we offer you, including customized Recommendations, advertising and currency display, to improve marketing, and to track access and use of ABP across the devices that you use to access ABP.
We have hired third parties to provide us information, reports and analysis about the usage, browsing patterns of our users. They may independently record the type of device and operating system you are using, general location information, as well as events that occur within our apps, such as how often you use our apps.
Location Information. Some of our mobile applications can deliver content based on your current location if you choose to enable that feature of the app. If you enable the location-based feature, your current location will be stored locally on your device, which will then be used by the app. If you elect to have a location-based search saved to your history, we will store that information on our servers. If you do not enable the location-based service, or if an app does not have that feature, the app will not transmit to us, and we will not collect or store, location information.
The ads in our apps are not targeted to you based on your current GPS location, but they may be targeted to you based on your ZIP code or device's IP address.
Third Parties
Some of the services and advertisements included in ABP, including on ABP and within our mobile apps, are delivered or served by third-party companies, which may collect information about your use of ABP.
These companies may place or recognize cookies, web beacons or other technology to track certain non-personal information about our website users. For example, in the course of serving certain advertisements, an advertiser may place or recognize a unique cookie on your browser in order to collect certain information about your use of ABP. For another example, an advertiser or ad server may also be able to collect your device's unique identifier in the course of serving an ad. In many cases, this information could be used to show you ads on other websites based on your interests.
We do not have access to, nor control over, these third parties' use of cookies or other tracking technologies or how they may be used.
Please click here to see a list of third parties that may be using cookies to serve advertising on our websites or in our apps. For example, we use Google to serve advertisements onto ABP, which use the Google Doubleclick cookie, and in some cases, a unique device identifier, to show you ads based on your visit to ABP and other sites on the internet. You may opt out of the use of the Google Doubleclick cookie by visiting the Google ad and content network privacy policy.
You have choices about the collection of information by third parties on our website:
1) If you would like more about your option not to accept advertiser cookies, please click here.
2) If you would like to opt-out of having interest-based ad targeting, click here.
Your access to our websites should not be affected if you do not accept cookies served by third parties.
WHAT DO WE DO WITH THE INFORMATION WE GATHER ABOUT YOU?
Provide the Services You Request
We use the information we gather about you to enable your use of ABP and fulfill your requests for certain products and services, such as sending out electronic newsletters and enabling you to participate in and renew paid services, polls, contests and message boards.
Statistical Analysis
We perform statistical, demographic and marketing analyses of users of ABP, and their subscribing and purchasing patterns, for product development purposes and to generally inform advertisers about the nature of our subscriber base. We use this information for analysis purposes, including analysis to improve customer relationships.
Customizing Your Experience
We use the information that we collect to allow advertising to be targeted to the users for whom such advertising is most pertinent. We also use this information to customize certain features of ABP to provide you with an enhanced experienced based on the type of device you are using to access ABP, and in certain cases, provide you with requested services.
Relevant Advertising
We may use demographic and preference information to allow advertising on ABP Service to be targeted to the users for whom they are most pertinent. This means users see advertising that is most likely to interest them, and advertisers send their messages to people who are most likely to be receptive, improving both the viewer's experience and the effectiveness of the ads. We disclose information to third parties only in aggregate or de-identified form.
Email Newsletters
ABP will periodically send you email newsletters or promotional email about services offered by ABP and its advertisers. For details about ABP email, please see below:
WHAT IS OUR EMAIL POLICY?
We will not send you marketing messages if you have unsubscribed. You can choose not to receive messages in the future by following the "unsubscribe" instructions located near the bottom of each email. We will not share, sell, rent, swap or authorize any third party to use your email address for commercial purposes without your permission. However, we will only share your email id with our registered partners in conformance with law. If you feel you have received an email from us in error, please contact newsletter.feedback@abpdigital.in
Email Newsletters. Anandabazar offers several email newsletters. If you no longer wish to receive a specific newsletter, follow the "unsubscribe" instructions located near the bottom of each newsletter.
Survey Email. We may invite you to participate in user surveys asking for feedback on anandabazar.com and existing or prospective products and services, as well as information to better understand our users. User surveys greatly help us to improve our Services, and any information we obtain in such surveys will not be shared with third parties, except in aggregate form.
Emails from You. If you send us an email, we will use your email address to respond directly to your questions or comments.
Email This Article Feature. Addresses you provide in the "Email" share feature may be saved for your convenience for future articles you may wish to email; but they are not used for any other purpose, and will not be shared with any third parties.
WITH WHOM DO WE SHARE THE INFORMATION THAT WE GATHER?
Within ABP
If you have registered to use ABP, we will not sell, rent, swap or authorize any third party to use your email address without your permission.
In the future, we may sell, buy, merge or partner with other companies or businesses. In such transactions, we may include your information among the transferred assets.
Third Parties
Not with-standing, anything contained herein above, we may share the information provided by you with third parties (in any manner whatsoever) and such consent for sharing information with third parties maybe expressed and / or implied as may be applicable and / or indicated. For abundant caution, it is provided that your participation in our website in any form and / or manner whatsoever is an implied consent from your end to be bound by our privacy policy and a further implied consent of allowing us to share your information with third parties.
If you are a print subscriber, we may exchange or rent your name and mailing address (but not your email address) and certain other information, such as when you first subscribed to ABP with other reputable companies that offer marketing information or products through direct mail. If you prefer that we do not share this information, you may opt-out by emailing us at support@abpdigital.in, reach out to us here. Or write to us at: ABP Pvt. Ltd. 6, Prafulla Sarkar St. Kolkata-700001, West Bengal, India.
Please include your account number and phone number in the body of your email or letter, and include "Opt-out" in the subject line.
We may share information about attendees to our live events with sponsors or other third parties. If so, we will notify you when you provide us the information.
Service Providers
We contract with other companies to provide services on our behalf, including credit-card and billing processing, ad serving, shipping, email distribution, list processing and analytics or promotions management. We provide these companies only with the information they need to perform their services. These service providers are restricted from using personal information in any way other than to provide services for ABP, and they may not share, resell or use the data for their own direct marketing purposes.
We reserve the right to disclose your opt-out information to third parties so they can suppress your name from future solicitations, in accordance with applicable laws. We may occasionally release personal information as required by law, for example, to comply with a court order or subpoena.
HOW DO I CHANGE OR UPDATE MY PERSONAL INFORMATION?
Manage Your ABP Account in the My Account Area. You may review and update your ABP membership or account information and access your transaction history in the My Account area. We will respond to inquiries regarding deletion of data within a reasonable timeframe.
Data Retention. We will retain your information for at least as long as your account is active, as needed to provide you services or as necessary to comply with our legal obligations, resolve disputes, and enforce our agreements. As a matter of course, we will delete personally identifiable information associated with accounts that have been inactive for at least 15 years.
HOW DO I OPT-OUT?
If, at any time, you prefer not to receive email marketing information from us, simply follow the unsubscribe options at the bottom of each email.
If you experience difficulty with the unsubscribe process, feel free to contact us at support@abpdigital.in and provide your email address along with the name of the newsletter from which you would like to unsubscribe.
Mail or Telephone Promotions
If, at any time, you prefer not to receive mail or telephone solicitations originated by ABP Home Delivery Department, or if you prefer that we do not share this information with third parties for marketing purposes, please email us at support@abpdigital.in or write to us at ABP Pvt. Ltd. 6, Prafulla Sarkar St. Kolkata-700001, West Bengal, India. Please include your account number and phone number in the body of your email or letter, and put "Opt-out" in the subject line.
It is further provided that if you wish ABP to delete your data provided by you to ABP you are requested to send an email to support@abpdigital.in by expressly stating that the data provided by you be deleted. However ABP can only delete the data you provided to ABP and this deletion shall in no manner deem to be deletion of your data that you may have provided to your linked third party social media accounts.
Use of Third Party Personal Information
If you choose to use "email this article" or give a Gift subscription, we require the recipient's name and email address. We will automatically send them a one-time email about the service. ABP does not store this information.
IS MY INFORMATION PROTECTED?
To prevent unauthorized access, maintain data accuracy and ensure the appropriate use of information, we have put in place commercially reasonable physical, technical and administrative controls to protect the information. Please note that no method of transmission over the internet, or method of electronic storage, is 100% secure.
OTHER INFORMATION
Compliance With Legal Process
We may access, preserve and disclose personal information if we are required to do so by law or we have a good faith belief that such action is necessary to (1) comply with the law or with legal process; (2) protect and defend our rights and property; (3) protect against misuse or unauthorized use of ABP; or (4) protect the personal safety or property of our users or the public (among other things, this means that if you provide false information or attempt to pose as someone else, information about you may be disclosed as part of any investigation into your actions).
Changes to This Policy
We evaluate this privacy policy periodically in light of changing business practices, technology and legal requirements. As a result, it is updated from time to time. Any such changes will be posted on this page. If we make a significant or material change in the way we use or share your personal information, you will be notified via email and/or prominent notice.