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Did you know that NASA conducted a study of the effects of spaceflight on twins. This was done to test Einstein's famous twin paradox experiment which is a result of relativity. Identical twins Scott Kelly and Mark Kelly were chosen and while Mark stayed on Earth, Scott spent a year aboard the international space station. You can read the results here.
What exactly is twin paradox? Let us understand Einstein's original idea first.
Surely the idea of time machine takes our mind on a wild imaginary ride when we attempt to understand it. Time travel is a kind of travel not in space (which we know has three dimensions, length, width and height) but it is the travel in the fourth time dimension. Is it possible to travel in the past or in the future?
In non-relativistic or classical physics, the concept of time is that of absolute time, which is independent of any observer and is same throughout the universe. Same time flow on Jupiter as on Earth. This was thought of first by English scientist Sir Isaac Newton back in the day... who proposed that time progressed at consistent pace for everyone everywhere and is essentially imperceptible and mathematical in nature.
But in Einstein's relativity, time is not absolute. Meaning that time is perceivable and is not the same everywhere and for everyone. And we now know that the rates of time actually run differently depending on relative motion for different observers; time effectively passes at different paces so it might not be the same flow of time on Jupiter.
So, making a time machine might be possible if we can control the flow of time.
There are two types of time travel: to the future and to the past. We already are moving into the future all the time at the tick of the seconds hand, but we're doing so at a regular rate. Could we make it so that this pace of time going forwards is increased, such that we go into the unseen future?
There is a way. Sending elementary particles on round trips in a particle accelerators at 99% of light speed is routine. The result is that the inner clock of such a travelling particle, say electron, runs much slower than that of a particle of the same species that remains at rest. Time slows for the fast moving particle.
Can this result from subatomic particles extend to larger human bodies? Einstein thought so... in his famous experiment "twin paradox" while he was working on the theory of relativity. In this, a hypothetical astronaut returns from a near-light speed voyage in space only to find his stay-at-home twin many years older than him, because travelling at high speeds has allowed the astronaut to experience only, let's say, one year of time, while ten years have gone by on the Earth.
The real paradox happens from the fact that there is "no favourable reference frame" in relativity. Why can’t the twin in the spaceship define himself as being at rest, let's say? And everyone on Earth is moving in that frame, oppositely. The Earth moves away at high speeds before returning to the still spaceship.
And if that is the frame, couldn’t the travelling twin apply time-dilation to everyone who stay on the Earth? By that argument, shouldn’t it be the humans of earth that remain younger once the twins are reunited? We all must eventually agree though that only one of the twins' perspective has to be the correct one. Which one is it then? So this is the actual "twin" or "dual" paradox of time dilation as put forth by Einstein in the 20th century.
Mind bending.
From general relativity, we can say that time passes more slowly for objects in strong gravitational fields than for the objects which stay far from such fields. There are all kinds of space and time distortions near black holes, where the gravity can become very intense. Thus if one of the twins is orbiting around a black hole and the other's orbiting around the earth the question of the paradox, "which twin is older" is answerable.
We have all watched "Back to the Future" and wondered how messed up it could get if we too did actually move backwards in time? And many scientists say the very premise of pushing a button and going back to yesterday violates the law of causality. However there are also some who think otherwise. Professor Michio Kaku has said, "Time is a river. It speeds up, meanders, and slows down. It can also have whirlpools and even fork into two rivers."
That last bit, "fork into two rivers," is important because then moving backwards in time could become at least thinkable. Because as soon as we push the button we go back into an alternate world or reality. We do not cause harm to our previous reality as in the case of "grandfather paradox". The idea was first proposed by British physicist David Deutsch who used the terminology of multiple universes to solve the grandfather paradox. Deutschian time travel involves the time traveler emerging in a different universe other than his own but very similar to his own.
Time travel will remain only conceptual and debatable except if we are able to develop enough advanced technology for it to become achievable. Until then we will use our earth bound telescopes as time machines. Because when you look into one you'd actually be looking into the past stages of the universe.. meaning that the star you observe today might not even exist in the first place. Turns out that if aliens knew exactly where to point their telescopes they could see dinosaurs at least in principle.
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credit: Geralt on pixabay |
Science without religion is lame and religion without science is blind. This popular quote of Albert Einstein has been repeatedly used, particularly in science versus religion debates. But from this statement alone can one say that Einstein was arguing for religion? A large number of believers definitely think so, referring to this adage and thus claiming the greatest scientist of the 20th century as one of their own.
However, Einstein had also famously written: "The idea of a personal God is a childlike one," in a letter to a friend dated 28 September 1949.
Einstein even went on to say, "You may call me an agnostic but I do not share the crusading spirit of the professional atheist whose fervor is mostly due to a painful act of liberation from the fetters of religious indoctrination received in youth."
From this saying alone, we can conclude that Einstein was neither a religious man in the usual sense nor was he a staunch atheist. Einstein was agnostic in belief. If you think about it, agnosticism really is the essence of science, whether ancient or modern.
Being an agnostic simply means that a man shall not say he knows or believes that which he has "no scientific grounds" for professing to know or believe.
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Does God play dice? (Einstein's most famous quote) |
Einstein was expected to make many statements on the origin of life, the universe and existence of God. Some of the views resonated with religious groups, but that does not make Einstein a believer. Albert Einstein was in fact one of the most famous agnostics in America, others being Edwin Hubble, Carl Sagan, John Bardeen, etc. and yet Einstein's name and his quotes are selectively chosen as merely "tools" by debaters to silence an opposition.
What had Einstein meant really, when he said: Science without religion is lame and religion without science is blind?
Actually, he was making a reference to a large part of human history in which science and religion were intertwined or interdependent. He put it like this, indicating that the interdependency still existed in the modern society.
This does not suggest in any way that Einstein was a deeply religious person and nor does it provide any surface to anyone to interpret it in such a way. If truth be told, Einstein had strongly asserted in one of his statements - "The word god is for me nothing more than the expression and product of human weaknesses."
So if Einstein wasn't even religious in the most ordinary sense, why his name is often dragged in trivial debates? Because it is assumed by a large number of people that in science "Einstein" is the authority. But they are wrong, because in actuality there is no authority in science. Feynman said: You can be the most amazing minds, if your ideas do not agree with experiment it is wrong. No matter who you are.
This is precisely how science progresses, by challenging, by having no authority, by questions and doubts; whereas religion has not progressed for hundreds and thousands of years.
Einstein's views were simply, that nature is not nurtured. That nature itself is nurturing. This is the ultimate essence of Spinozism a philosophical system which was largely advocated by Einstein. Spinoza belief is the unbounded admiration for the structure of the world, the universe, so far as our science can reveal it.
Just a year before his death, Einstein had replied to a fan in a letter, "It was of course a lie what you read about my religious convictions, a lie which is being systematically repeated. I do not believe in a personal God and I have never denied this but have expressed it clearly."