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the same thing could have been said about the discovery of Neptune [1]: "there's no evidence a planet is there, it's pure speculation. The changes in Uranus' orbit must be the result of mathematical error and not another planet."

[1] https://en.wikipedia.org/wiki/Neptune

If man had discovered Gravitational Lensing BEFORE Einstein had formulated General Relativity we would have given some name to the effect, and perhaps even considered it a characteristic relationship between stars and light. The relationship happens to be an INDIRECT one. Star mass bends space, and the light merely "appears" to bend, when it traverses that space. It doesn't actually bend.

What I'm saying about Dark energy/matter, is that there is also an INDIRECT relationship there. It's not just a special invisible mass and invisible energy. It's a fundamental misunderstanding about what spacetime is. I think the "dark" quantities are every bit as much an illusion as the "light bending" illusion created by stars.

> Star mass bends space, and the light merely "appears" to bend, when it traverses that space. It doesn't actually bend.

On the contrary, it actually bends. Spacetime curvature is a real, not an apparent, effect.

"Spacetime tells matter how to move; matter tells spacetime how to curve." -- John Wheeler

More on this topic: https://en.wikipedia.org/wiki/Einstein_ring

The light is traveling in a straight line ALWAYS, but merely appears (to us) to bend, because the space it's traveling thru (in a straight line) is itself bent. The space itself is bent. The light goes straight.

That's the distinction i was attempting to point out, when I said if mankind had visually noticed star-induced 'lensing' (before Einstein explaining what to expect) we would have ASSUMED the light itself was bending, and that space was 'flat' (unbent). Thinking space is flat and light is bent (the opposite of what is true), would have been the same kind of blunder we are making today believing that Dark matter/energy is actually real.

> The light is traveling in a straight line ALWAYS, but merely appears (to us) to bend, because the space it's traveling thru (in a straight line) is itself bent. The space itself is bent. The light goes straight.

Space is curved, and the light passing through it is also curved. That was the point of my link to the Einstein Ring page -- to show that light is in fact curved along with space.

The first important confirmation of GR was an experiment conducted in 1919 that showed curved light paths of starlight passing near the sun, observed during an eclipse.

If you happened to be located near a black hole, at 1.5 times the radius of the event horizon, by looking along a tangential path, you would see the back of your own head, regardless of which direction you looked. The reason? Light is curved along with space.

It's not accurate to say, as you are doing, that light always follows straight paths. It is accurate to say that light follows the curvature of the space through which it passes.

> ... would have been the same kind of blunder we are making today believing that Dark matter/energy is actually real.

Try to avoid moving ahead of the evidence. The present evidence is that dark matter and energy are real, again following Occam's razor. But I can't say these things are real as a matter of concluded fact, and you can't say they aren't. No one knows, and science requires us to wait for observation and theory to sort it out. Science doesn't progress by proclamation, but by way of theories that resist sincere efforts at falsification.

Apropos: https://youtu.be/b240PGCMwV0?t=37

I do understand why you think what you do. Most physics articles (and even the Wikipedia page on Gravitational Lensing) are explaining it wrong. They are saying that the light bent. That's not what's really happening. The light doesn't bend relative to the space it's flowing thru. It flows in a perfectly straight line. Gravity has no direct effect whatsoever on light, because light is massless. Gravity only can effect the SHAPE of the spacetime density field. The fact that the spacetime is bent makes it look to us, as if the light changed direction. It didn't. Light passing thru an ordinary optical glass lense DOES bend, but light passing by a massive object in space absolutely does not bend. It merely "looks" like it did.

> Most physics articles (and even the Wikipedia page on Gravitational Lensing) are explaining it wrong.

Ah, the encyclopedias are wrong. That may be true, but only if you meet your burden of evidence. You cannot meet your burden of evidence, and you show no sign of even trying.

Oh, I can prove it with evidence. The only thing that can change the direction of motion of a particle is a force. Photons have zero mass and zero charge, therefore no force (including gravity) can act on light (strong and weak interactions are not applicable here). Therefore light will always travel in a straight line. When light appears to 'bend' it is not because the light itself changed direction in its reference frame, but because the space the light is traveling thru in is warped. Any physics professor will understand precisely what i'm saying, and all agree. Someone who has only read a few articles online will not. I've understood this since 1986. I'm very old and wise you little child.

> The only thing that can change the direction of motion of a particle is a force.

Quite false. You're overlooking the fact that photons are the carrier particle of the electromagnetic field, which takes the form of waves in space -- waves that change direction without the application of forces. An optical lens changes the direction of photons without exerting a force. So does curved spacetime. These are examples of hundreds of things about physics that contradict your outlook.

Also, masses respond to gravity by changing direction, and gravity is not a force: http://curious.astro.cornell.edu/physics/140-physics/the-the...

Again, at 1.5 times the radius of a black hole, looking tangentially, you would see the back of your own head. So even in this local frame of reference, light has taken a curved path along with curved spacetime. In other frames of reference, light is obviously not traveling in straight lines. In fact, it can be argued that light never travels in straight lines -- that would be true only in a universe without any mass at all.

You could argue that water always travels along straight lines inside a pipe and never changes direction, and in the case of the pipe itself changing direction, you could argue that the water is always traveling in a straight line from its own perspective inside the curved pipe, but having said that, people would see your ideas for what they are.

> Any physics professor will understand precisely what i'm saying, and all agree.

You appear to have forgotten I have already disproven this with my John Wheeler quote: "Mass tells space-time how to curve, and space-time tells mass how to move." As with masses, so with photons. If masses could travel at c, they would take the exact path photons do -- curved ones.

> The only reason there's two kinds of "dark" is because both the space aspect (matter) of our math is wrong AND the time aspect (energy) is wrong.

You're pairing space and matter, then time and energy, and comparing them as though these entities are naturally paired in current theory. They aren't. Space and time are elements of spacetime, matter and energy are interchangeable by way of a rather well-known equation, but these things don't arrange themselves as you're trying to do.

> And as for your last sentence, trust me I understand the scientific method, and how proof, evidence, and fact interrelate with knowledge.

So you didn't say, "So many non-scientists think dark matter is proven. It isn't. It's nothing but pure conjecture."

Nothing is ever proven in science (falsified, yes, proven, no). And dark matter and dark energy are both more than "pure conjecture," a domain reserved to notions lacking observational evidence.

I should have been clear that I'm not making a distinction between energy and matter.

Come on. Is it so hard to say "Oops I mixed them up"?

I also use the words "space" and "time" independently as if they were separate things, when I know full well every last detail about SR/GR (being an engineer myself). So yes, only in the context of discussing "dark stuff" I will lazily interchange matter and energy. Only on HackerNews do I ever encounter the type of ass-holes who will parse sentences intentionally wrong as to yield the incorrect conclusion. You are one such person.

> Only on HackerNews do I ever encounter the type of ass-holes who will parse sentences intentionally wrong as to yield the incorrect conclusion. You are one such person.

Troll alert. Space and time are elements of spacetime, they are an integrated whole, a fact first pointed out by Einstein's math teacher Minkowski. When Einstein first read what Minkowski had written, he said, “Since the mathematicians have invaded the theory of relativity, I do not understand it myself anymore.”

Only later, after learning tensor calculus and beginning work on GR, did Einstein understand what Minkowski was going on about. But in those days people were interested only in getting it right, not posturing as right even when they're wrong.

Nice dissertation on 2+2=4. I've known relativity for 30years. The point i was making (as i'm sure you genuinely DO actually know, despite pretending once again to need to correct me), is that even physics professors in the middle of physics lectures will say "space" or "time", depending on context. Learn the fact that English and all languages have syntactical nuances. Oh,and thanks for the warning that you are a Troll, but I don't mind. I'm biting the hook. Nothing thrills me more than debating physics. Thus the 30yrs.

> Nothing thrills me more than debating physics.

You aren't debating physics.

Troll alert.

Please don't resort to name-calling, regardless of the language used by fellow commenters.

It's not name-calling. This person really is a troll, a term with an unambiguous definition: http://www.urbandictionary.com/define.php?term=troll . He tries so hard to earn the label that it seems unjust to withhold it.

In the days of Usenet, before there was an Internet, this sort of language was regarded as neutral and informative -- it's not abusive when it's accurate. But the Politically Correct movement in social media is seeing a revival, such that even accurate use of these terms is regarded as counterproductive.

In the Usenet era, some individuals would strive to earn the label, and applying it would save people a lot of time trying to engage in constructive conversations with people who were manifestly unable to rise to the occasion.

Bottom line -- it's possible to take PC to a pointless extreme. And I'm hardly the first to make this point.

If they're a troll, don't feed them. That goes back to Usenet as well. There's never a reason on HN to be uncivil.

> There's never a reason on HN to be uncivil.

Fair enough, but this begs the question of what constitutes incivility. If present trends continue, telling someone that they're wrong will be regarded as uncivil behavior. To avoid censure it will only be possible to assert that they've posted "alternative facts."

I happen to agree that incivility represents a real problem in social media, and we've seen many sites abandon their discussion groups because of uncivil posts and people. But I think the argument can be made that definitions have changed as well as behavior.

> That goes back to Usenet as well.

Not really. Having posted there for many years, I can tell you from direct experience that the perceived threshold of incivility has changed completely. One need only review posts from that era to see the point that definitions and standards have changed.

But this is now, and an argument about what was once acceptable doesn't seem particularly persuasive even to me, especially now that we have an embodiment of incivility running the country.

Just to keep score: You called me a troll, because I called someone an a-hole, for calling me a liar. That's what just happened. What a totally PC Snowflake Soap-Opera. Of course that's based on the assumption that the 'Sock Puppet' burner accounts aren't BOTH YOURS to begin with. hahahahaha. omfg that would be hilarious. In case it doesn't even matter, i'm using my REAL identity.

Only on HackerNews do I ever encounter the type of ass-holes

No matter how egregious the behavior of your fellow commenter, it's never okay to resort to uncivil language ourselves.