Genady

Exactly: 'now' is ill-defined and a notion of 'exists' that is attached to 'now' is thus ill-defined. Inevitable or not, there is only one factual future. That's why I think it is meaningful to say about an event that it exists or doesn't exist in the future.

No, and observations show that it does not.

As I see it, past exists in the past, future exists in the future, and whatever exists now exists in the present. If one defines 'exists' as existing necessarily now, then it leads to a contradiction, by definition, but I don't see a justification to this kind of definition.

Yes! Example: Israel.

(Dimension - Wikipedia) To specify an event, we need 4 coordinates. Thus, a space of events is 4 dimensional. These dimensions are 3 spatial and 1 temporal coordinates. I think it is this straightforward.

Correct This is a comprehensive article.

Where? Reference?

What is meant by a "product"?

1. What is an invisible image? 2. How do we, or them, know that they form invisible images? PS. I assume that aphantasia refers to inability to form any kind of mental images, visible and invisible. PPS. I know you cannot reply now because you've used up your five posts limit of the first day here.

I suspect that the emphasis of OP is not on the word 'real' but rather on the word 'condition.' IOW, aphantasia is a phenomenon, but not a condition.

In 8 billion brains, all individual and different, one perhaps can find about all imaginable variants as long as they are functioning.

Well, I have this "unreal" condition. I can force myself to make a mental image of something, but normally I don't bother with mental images. Texts and formulae are a different story. I see them on my "mental screen" all the time.

I don't think so. I don't think there is such a difference. And, anyway, they all had the same handedness.

This would be good but would not apply like this in that specific case. Here what it was. I've found that wire black corals on Bonaire reefs always make a right-handed helix (as discussed here: Wire Black Coral helix ? - Evolution, Morphology and Exobiology - Science Forums). I've asked in the email to one of the researchers who published papers about this species if this phenomenon has been observed before. The person answered that it has not been observed because from their experience these corals make right- or left-handed helices randomly, "like in the photographs attached." Four underwater photographs were attached. All four showed right-handed helices only.

This is a comprehensive article. Adds more constrains and limitations for evolution, development, and use of wheels in organisms to a few discussed. Also answers the exchange between @Sensei and @Moontanman above.

I had a peculiar experience with the situation as described in the OP, when the response was not only brief and polite but also evidently wrong. I didn't know what my next step then should be.

If this is not about the theory of relativity as in physics, then it should not be in the Physics forum. It should go elsewhere.

Try Aspirin.

No, Einstein didn't say this.

Stop here. They are not.

Two wrongs here: 1. It is not so according to Einstein. 2. It is not what Einstein called, the happiest thought.

Yes, it looks so. This is about what And And what Dawkins wrote in 1996 (I just repeat it here as it has been quoted above):

Yes. These wheels appear as cellular components. But not as components of a multi-cellular organ. I think that both Dawkins and @mistermack have explained it well. (It's fun to imagine an aquatic animal that moves by such a motor.)

However, such a design works in bacteria. Not a human design, with a spinning wheel, powered by and made of the bacterial components. PS. Not for moving blood, of course, in bacteria, but for a different function.

Turned out that Richard Dawkins wrote an article 26 years ago exactly about this question. (Why Don't Any Animals Have Wheels? | Live Science)