• Question: do you believe in the big bang theory and if you do why but if you don't then also why?

    Asked by anon-217175 to Savannah, Philippe, Lucy, Joanna, Harrison, Edoardo on 12 Jun 2019.
    • Photo: Joanna Huang

      Joanna Huang answered on 12 Jun 2019: last edited 12 Jun 2019 2:44 pm


      Yes absolutely. I believe in it because there is a lot of scientific evidence backing up the theory. It has been tested many times and data have shown to agree with it – it is also a theory that is falsifiable, meaning it can be proven wrong. So far, that hasn’t happened!

      One piece of evidence for Big Bang – almost all of these galaxies are moving away from us! And at speeds of hundreds of thousands km/s :O.

      If most galaxies are moving away from us, it means that the Universe is expanding. If the Universe is expanding, then in the past it must have been much smaller. Go back far enough, and there was a moment when all the matter in the Universe was packed into a point and expanded outwards. That moment was the Big Bang.

    • Photo: Harrison Prosper

      Harrison Prosper answered on 12 Jun 2019:


      I don’t “believe” the big bang theory! Scientists generally don’t believe theories. They accept theories if the evidence supports these theories. More importantly, we reject theories that are not supported by the evidence. For example, there are people who actually believe the Earth is flat. I don’t accept that because the evidence is overwhelming that the Earth is almost a perfect sphere. The evidence is so overwhelming in fact that I believe the Earth is indeed round! I accept the big bang as the theory of the Universe that best agrees with the evidence. It could well be that we shall conclude one day that the big bang theory is wrong because it disagrees with observations. But, so far, the idea that the Universe began in a super dense, extremely hot, state called the big bang explains a great deal of data. By far the most striking prediction of the big bang theory is that, today, the Universe should be filled with microwaves at a temperature of 2.7 degrees above absolute zero. The microwaves are called the cosmic microwave background (CMB). The data agree perfectly with the prediction. The microwaves that we measure today are the afterglow of the light created 14 billion years ago in the big bang. The theory also predicts that the universe should be about 75% hydrogen and about 25% helium with trace amounts of everything else. This agrees with observations. The theory predicts that tiny differences in temperature of 1 in 100,000 from the 2.7 degrees are caused by tiny differences in the density of matter when the Universe was about 350,000 years old and that these tiny differences (called density fluctuations) are the seeds of galaxies. Amazingly, we can measure these minute temperature differences across the sky by measuring the CMB temperature very, very, precisely. When these measured differences are translated into matter density differences and evolved on a computer from 350,000 years to the present time, 14 billion years later, it is found that the predicted distribution of galaxies matches the observed distribution. And so on. It is all of these successful predictions that makes me accept the big bang theory.

    • Photo: Edoardo Vescovi

      Edoardo Vescovi answered on 12 Jun 2019: last edited 12 Jun 2019 8:01 pm


      I don’t believe, rather decided to trust the scientists who tested this model. There are many steps in this sentence, which I try to sketch.

      1) The big bang is part of a model (also called theory) that tries to explain how the universe came out of nothing. As the first event by definition, no human could possibly be there to witness the big bang according to this model. Can’t we say anything about the past until prehistory then?
      2) As a scientist, certainly not. We can test the model of the big bang. It must have left some traces after all. These are listed in an answer above and what we observe is in line with them.
      3) You can still complain that neither you nor me has taken the time to observe the sky. Here comes the assumption that scientists who observed did their job fairly.

      You come to a different conclusion if you don’t agree with all points. For example, propose a different model (instead of 1), not follow the scientific method (for 2) or trust other people (for 3).

    • Photo: Savannah Clawson

      Savannah Clawson answered on 12 Jun 2019:


      Yes I do believe in the Big Bang because it is the best theory we have today that matches our observations of the Universe. Science is all about coming up with theories that match the evidence in front of you – you could create the most beautiful and clever theory but it means nothing if it doesn’t agree with experimental evidence!
      .
      The Big Bang theory is able to predict and explain what we see in the Universe but it also has some problems. For example, the Universe is incredibly similar no matter where you look – in fancy science words we say it is “homogeneous” and “isotropic” which basically means it looks the same in all directions and is the same no matter where you are looking from. We don’t know how this could have happened without all parts of the Universe being able to talk to each other at once in the past – this violates one of our most important laws of physics saying that nothing can go faster than the speed of light. The Universe is also incredibly flat which requires special conditions to be set at the Big Bang – we don’t like special conditions in physics unless we have a reason for them to be there! To get around all of this, we have to add extra conditions onto the Big Bang called inflation – this is a period of really really quick expansion that happened just after the Big Bang itself. Now inflation is great but it actually creates more problems than it solves which is a whole other conversation topic!
      .
      So for now, I believe the Big Bang theory because it is the theory that best agrees with our evidence. However, I will be willing to go against it if a better theory comes along in the future!

    • Photo: Philippe Gambron

      Philippe Gambron answered on 14 Jun 2019:


      The theory is convincing because it is backed by evidence. When we look at galaxies, we realise that they are receding away from us and the further away that are, the fastest they go. This means that, at some point in the past, the Universe was smaller, hotter and denser. The name big bang was in fact coined to deride the theory but, now, everyone is convinced of it. There is further evidence for it. For example, everywhere in the sky, there is an afterglow of microwave which is a remnant of the epoch where the Universe was very hot.

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