In Einstein's equation, time is a river. It speeds up, meanders, and slows down. The new wrinkle is that it can have whirlpools and fork into two rivers. So, if the river of time can be bent into a pretzel, create whirlpools and fork into two rivers, then time travel cannot be ruled out.
Interpretation
Time is not a fixed entity but rather a fluid concept that can be manipulated and understood differently.
This quote by Michio Kaku illustrates the complexity and malleability of time, suggesting that our understanding of it is far from linear. It compares time to a river that can change its flow and direction, indicating possibilities like time travel, which challenges our conventional perceptions and encourages a broader exploration of the universe and theoretical physics.
In practice
In a lecture on theoretical physics, one might introduce this quote to spark discussion about the nature of time.
The Europeans and the Americans are not throwing $10 billion down this gigantic tube for nothing. We're exploring the very forefront of physics and cosmology with the Large Hadron Collider because we want to have a window on creation, we want to recreate a tiny piece of Genesis to unlock some of the greatest secrets of the universe.
Cancer is like the common cold; there are so many different types. In the future we'll still have cancer, but we'll detect it very, very early, so that it won't kill anybody. We'll zap it at the molecular level decades before it grows into a tumor.
When you look at the calculation, it's amazing that every time you try to prove or disprove time travel, you've pushed Einstein's theory to the very limits where quantum effects must dominate. That's telling us that you really need a theory of everything to resolve this question. And the only candidate is string theory.
Consciousness-one level is understanding where we are in space. Consciousness two is where we understand our position in society: who's top dog, who's underdog and who's in the middle. And type-three consciousness is simulating the future. And type-three consciousness, only humans have this ability to see far into the future.
Some advice: keep the flame of curiosity and wonderment alive, even when studying for boring exams. That is the well from which we scientists draw our nourishment and energy. And also, learn the math. Math is the language of nature, so we have to learn this language.
After that cancellation [of the Superconducting Super Collider in Texas, after $2 billion had been spent on it], we physicists learned that we have to sing for our supper. ... The Cold War is over. You can't simply say "Russia!" to Congress, and they whip out their checkbook and say, "How much?" We have to tell the people why this atom-smasher is going to benefit their lives.
While the finish given to our picture of the world by the theory of relativity has already been absorbed into the general scientific consciousness, this has scarcely occurred to the same extent with those aspects of the general problem of knowledge which have been elucidated by the quantum theory.
There is much that science doesn't understand, many mysteries still to be resolved. In a Universe tens of billions of light-years across and some ten or fifteen billion years old, this may be the case forever. We are constantly stumbling on new surprises
If you aren't confused by quantum mechanics, you haven't really understood it.
The weight of evidence for an extraordinary claim must be proportioned to its strangeness.
The economists will have to revise their theories of value.
Let's not spend resources that we don't need to be sending astronauts back to the moon. Let's not spend expensive resources on bringing people who have reached Mars back again. Prepare them to become a growing colony.
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