With all it’s vastness and complexity it’s taken a long time for humans to reach the understanding that we have of the universe that we have. This is the story of evolving understanding and how simplicity gives way to incredible truth’s that seems to sit at odds with how we think life should be… and we’ve only just begun our journey of understanding.
Abstract Ideas
After the Michelson Morley experiment and it’s famous ‘no result’ it was about 25 years before the crisis in physics would get resolved. The thinking came from a young man in his twenties who was very good as visualising abstract ideas and coming up solutions to abstract problems. This man was Albert Einstein and key to resolving the lightspeed problem was in 2 questions he asked himself:
1) “If I ran alongside a lightwave – what would it look like?”
2) (While shaving and looking in the mirror where he asked the question) “If I was to travel at the speed of light towards the mirror, would it turn black?”
And it was from these thought experiments that came a simple theory that would solve the problem of ‘in what reference does light move at speed c’ and yet this simplicity would lead to some staggering and incredible insights into understanding the universe.
What Einstein said was this:
“The laws of physics is the same for all observers in uniform motion.”
Einstein’s Relativity Theory
In essence this took the Galileo / Newton laws of relative motion and added electromagnetism onto the end of it.
To make his theory apply to electromagnetism he backed this up by saying:
“The speed of light is the same for all observers in uniform motion”.
The theory of Special Relativity is called special not becasue it’s special in some grandiose way it’s becasue it applies to a special set of circumstances and that circumstance is for observers in uniform motion that is that they are travelling in a straight line at constant speed.
This simple theory (which it has to be said is one of the most tested theories in science and is no longer ‘simply just a theory’) is in itself not that difficult to acknowledge. It means that whether on Earth or in a jet plane or on a spaceship travelling at half the speed of light or a distant galaxy travelling away from Earth at nearly the speed of light – the laws of physics including electromagnetism will be the same.
What this does though is it does strange things to space and time.
Strange things in Space and Time.
The speed of light (c) is is around 300,000 kilometers (186,000 miles) per second, the exact figure 299,768,458 kilometers per second. In fact the metre is now defined by the speed of light not the other way around – a metre is defined as the distance light travels in 1/299768458 of a second or in old measurements a foot per nanosecond (billionth of a second).
What the relativity says is that if I was to take a standard measure and a very accurate clock and use physics to measure the speed of a lightbeam where:
Distance (D) = Speed (V) times Time (T)
If I measure the speed of light on Earth with this clock and measure and then take it on a jetplane travelling at 600mph and measure the speed if light it would be the same if I measure the speed of light on the spaceship travelling at half the speed of light or the distant galaxy travelling away from us at near light speed I would get the same result. The speed of light – 299,768,458 metres per second.
Even more mind blowing is the fact that the speed of light would be the same for any observers in uniform motion – “Even if those observers are travelling at different speeds with respect to each other”.
How is this even possible?
How can the speed of light be the same in all these reference frames. The simple answer to this is that measures of space and time are different in different reference frames.
Common Sense
How can this be true – out common sense screams when presented with these facts. Quite simply our common sense is based on how space and time operate in one reference frame – the Earth’s. If we were able to experience reality from different references then relativity would be more intuitive to us.
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Simon’s Space
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I think it was Brian Cox I was watching once, and they do think time travel is possible. But only forward, I think? No backwards. This was a long while ago though, lol
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In essence that’s the thing, moving forward in time is possible but not back. Which is kinda interesting in itself, just one way.
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Thanks for the explanation Simon, and especially for the last few words on Common Sense. I guess because we are wired to Three Dimensions and our 24 hour clocks (which I am told is only part of ‘Time’) most of us find these concepts so difficult to grasp.
The three pictures are magnificent, each in their own way, I’m stuck for choice.
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That’s the key thing to take from this… our perception is limited. Thanks Roger 🙂
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My pleasure Simon.
Keep up the good work👍
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So much of modern science is a matter of perspective. Quantum physics is common sense to atoms, and relativity is common sense to light waves and black holes.
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Quantum science is madness… I’ve never some across anything so strange lol
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