- #1
kronecker
- 19
- 0
i don't know much about physics but what do people mean by 'our universe is expanding' ? thoug we see the truth that no thing is getting larger/longer. what is the proof for this expansion ?
thanx
thanx
Very good explanation at the non-technical level, Chronos. It is important that people new to cosmology understand that the 20th century's (arguably) top mathematical theoretician and top observational astronomer were both ambivalent about some aspects of their own work (or the implications thereof). The air of certainty conferred on the standard model of cosmology should not preclude thoughtful inquiry into alternatives.Chronos said:Sticky wicket. As mathman pointed out, the short answer is most everything is running away from us [after 4.5 billion years wearing the same crust, the Earth tends to have that effect on other galaxies]. The thorn on the rose, is the universe is dynamic. It must either expand or contract to continue to exist for as long as it evidently has. Einstein was the first [most probably] to realize this. When he started working out the solutions to GR field equations, he reached a startling conclusion. The universe must ultimately collapse under the inexorable force of gravity. He viscerally rejected that premise on logical grounds... if the universe must collapse, there is no good way to explain why it has not already done so [hence rendering the entire question moot]. To do otherwise would confer a priveleged reference frame to our very own existence. Given his entire GR premise was based on background independence, he 'fudged' in a cosmological constant that restored the universe to a static, eternal state he was comfortable with [as well as 'mainstream' scientists back then]. He later abandoned that notion, with relief, when Hubble discovered the universe was expanding [despite the fact Hubble was never entirely satisfied with his apparent discovery]. Modern science has since restored the concept for lack of a better explanation that fit later observations. Cosmology is a fickle mistress. The three blind men who described an elephant using the braille system probably arrived at a better theoretical model than we have to date. That's what makes it fun.
A very good link! That paper is indicative of the uncertaincies that premier scientists held regarding their own work. Halton Arp wrote to me (nearly 20 years ago) that after viewing Hubble's papers, he saw a similar level of caution in Hubble's work, saying "IF redshift=distance" in Hubble's papers. That was a turning moment for me. We cannot codify the work of astronomers/cosmologists. There is too much left to be done.Chronos said:Indeed, agreed on all counts, Turbo. Some of the most legendary scientists of the past century or so were their own fiercest critics. This trait is not only admirable and desirable, it enhanced their contributions and facilitated general acceptance of their work. Here is a nice article.
http://www.punsterproductions.com/~sciencehistory/cautious.htm
I think, at least hope, this is the example followed by most modern theorists. They are probably less confident in their models than it sometimes appears. On the other hand, they have a better feel for where the good 'hunting spots' are than do we.
kronecker said:i don't know much about physics but what do people mean by 'our universe is expanding' ? thoug we see the truth that no thing is getting larger/longer. what is the proof for this expansion ?
thanx
My experience is that only about 5 in twenty will even consider a new idea unless it carries a known name. Only one in twenty will take the time to understand a new idea. If a known name presents a new idea there is usually a bandwagon that will follow no matter how stupid the idea is.It is certainly true there is more pressure to churn out new results than to drive another stake into the heart of prospects that appear unlikely to pan out. This approach, of course, assumes the risk of wasting time and resources barking up the wrong tree. On the other hand, the research that is done will eventually force them back onto the right path. If there are serious flaws in the model, it should collapse under its own weight at some point - and hopefully sooner than later.
Scientists, on the whole, tend to do a poor job explaining why they pursue one idea and not others. Their peers understand, and that's about all that matters to them. Unfortunately, the people who end up trying to explain it to the rest of us are lesser experts and occasionally give ambiguous, even bad information. This just fuels the fire, sometimes to the point people think they are being deliberately misled. There are also those who take advantage of this to promote their own agendas. Their motivations range from scamming for profit, feeding their own delusions, or simple puffery. These are the spiders that spin the web of deception. You don't have to google much to find them. Skepticism is your friend.
The current understanding is that the universe is expanding at an accelerating rate, meaning that galaxies are moving away from each other at faster and faster speeds. This expansion is believed to be driven by a mysterious force called dark energy.
Scientists use a variety of techniques to measure the expansion of the universe, including observing the redshift of light from distant galaxies, studying the cosmic microwave background radiation, and using Type Ia supernovae as standard candles. These methods all provide consistent evidence for the expansion of the universe.
No, the expansion of the universe is not uniform. In fact, in some regions of the universe, the expansion is faster, while in others it is slower. This uneven expansion is thought to be caused by the distribution of matter and energy in the universe.
The expansion of the universe is a key piece of evidence for the Big Bang theory. The theory states that the universe began as a singularity and has been expanding ever since. The expansion of the universe is also responsible for the cosmic microwave background radiation, which is considered the afterglow of the Big Bang.
It is currently believed that the expansion of the universe will continue forever. However, the rate of expansion may change over time due to the influence of dark energy. Some theories suggest that the expansion could eventually slow down or even reverse, leading to a collapse of the universe, but this is still a subject of ongoing research and debate.