Exploring the Universe - The 3 Fundamental Questions
The fundamental questions in science are as given under.
1. Is space finite or infinite?
2. Did time have a beginning at big bang and will it end?
3. Is time travel possible?
Seeking answers to these questions and exploring the universe is an exciting journey in understanding more about our origins.
Universe is vast and is probably beyond our scope to comprehend its functioning. We may still find few answers to the questions that have been baffling the mankind for long.
Gravity and Nuclear Force
A simple concept like gravity is difficult to comprehend. We know gravity as an attractive force that exists between two bodies. This force is directly proportional to the sum of the masses and inversely proportional to the square of the distance between the two bodies. But do we know why gravity has to be always attractive and not repulsive? How does gravitational force travel through space?
It is a mystery how Einstein arrived at the famous energy-mass equation. He says the missing mass gets converted into energy in a nuclear reaction. How did it occur to Einstein that the missing mass had to be multiplied by the square of the speed of light to calculate the energy thus released? There are so many mysteries in physics yet to be unraveled.
1. Is Space Finite or Infinite?
Man has been wondering for long if space is finite or infinite. Some scientists hold the view that space is finite. I find it difficult to subscribe to this view from a common man's perspective.
How does the end of space look like?
Let us assume that we are going on an imaginary journey towards the end of space. If we reach a dead end, then we need to conclude that the space is finite. We may conclude that the space is infinite if we do not hit a dead end. Our journey takes us past the solar system, our Milky Way galaxy and several other galaxies before we reach the end. We can realize the end point only if we know how the end will look like.
Will it look like a thick impenetrable wall? A wall may stop us from traveling further but it is still not the end. Will it be empty space beyond the endpoint? This still cannot be the end as space continues without matter. So our little thought experiment seems to indicate that space is infinite.
Can space be round and finite?
It is pertinent to point here that Stephen Hawking had proposed a stronger argument to the contrary. According to Hawking, the four-dimensional space-time can be finite just like the two-dimensional surface of Earth. We can never reach the end of the finite Earth no matter how far we go. The surface of the earth is round and one can never define an end.
The four-dimensional space-time can also be round and finite with no endpoint just like our planet. Hawking's analogy is difficult to comprehend for my simple mind. How will a round four-dimensional space-time look like? My head is already spinning trying to visualize the same.
2. Did Time Begin at Big Bang?
Did time have a beginning? Many present-day scientists say time did not exist forever, and it had a starting point at Big Bang. Few also seem to indicate that Big Bang is the earliest point of time we can know about. They say any past event would have no bearing on how things are now.
Assume I write something on a piece paper and then send it to a shredder. I might have written a poem, a story or some meaningless stuff on that paper. But once the paper comes out of the shredder as torn pieces, there is no way one can determine the worthiness of the contents written earlier. The shredding of paper is akin to the Big Bang moment. It erases the history.
Singularity and Explosion
The entire matter we see around us was once condensed and concentrated in a near singular point. The matter could not stay in such a dense state for a long period and then there was a violent explosion. This explosion is called the Big Bang event.
The matter as it exists today could collapse into a near singularity later. This gravitational collapse could lead to another Big Bang explosion. The near singularity, explosion, expansion and contraction are all part of the constant astronomical cycle of events. This cycle could be like other cyclical phenomenon such as the seasonal changes in a year.
In the never-ending cycle of events, time never had a beginning and would never have an end.
Never Ending Cycles
In the never ending cycle of events, time never had a beginning and would never have an end.
3. Is Time Travel Possible?
We all thought time was an absolute. This belief was broken when certain amazing observations were made regarding the speed of light.
Is Time Relative?
Assume I am in a train moving northward when another train traveling southward crosses my train. If I look at the passing train, it would appear that my train has been going at a much faster pace than its actual speed. Similarly, scientists were expecting the speed of light to be different for a source of light approaching as compared to a source that is moving away.
But to the surprise of everyone, the speed of light was the same for objects approaching us and also for objects moving away from us. What does this mean? We all know the simple formula that compares speed, distance and time.
Speed = Distance / time
If speed is a constant, then there could be some vague situations when time could change for two observers moving in an opposite direction. The mathematics involved here is complicated. It is enough if we appreciate that time becomes a variable when distance changes since speed of light is constant. It is difficult to understand how two clocks can run at different speeds unless there is a manufacturing defect in one clock. Time travel is a possibility if time is relative.
If time is absolute, there is no place for concepts like time travel. The only argument against the absolute time is the constant speed of light. We may need a better theory explaining how this speed can stay constant even when time remains absolute.
When a light source is moving towards or away from us, the light undergoes a change in wavelength leading to a redshift or blue shift in a spectrum. The relative speed of two objects gets manifested as a change in wavelength and so a future theory could explain that there is no need for the speed of light to change!
Theoretical Physics is an exciting domain that could unlock many more mysteries of the Universe in the coming years.
- Ethan Siegel. (2017, October 14). Ask Ethan: Is The Universe Finite Or Infinite? [Blog post]. Retrieved from https://www.forbes.com/sites/startswithabang/2017/10/14/ask-ethan-is-the-universe-finite-or-infinite/#3f6510184967
- Tosin Thompson. (2015, July 23). Is there such thing as the beginning and end of time? [Blog post]. Retrieved from https://www.newstatesman.com/sci-tech/2015/07/there-such-thing-beginning-and-end-time
- Cathal O'Connel. (2016, April 5). Five ways to travel through time [Blog post]. Retrieved from https://cosmosmagazine.com/physics/five-ways-travel-through-time