Evidence for 'Planet 9' may actually show our theory of gravity is incomplete

[Admin]

Evidence pointing toward the possible existence of “Planet 9” lurking at the edge of the solar system may actually mean we need to revise our recipe for gravity.

Evidence for 'Planet 9' may actually show our theory of gravity is incomplete : Read more

 

[jim15936]

A good alternate theory is that there is one or more small black holes in the Kuiper Belt, with event horizons the size of a tennis ball. So absent a very rare collision, it's invisible to us. From Wikipedia article on primordial black holes:

"In August 2019, a study was published opening up the possibility of making up all dark matter with asteroid-mass primordial black holes (3.5 × 10−17 – 4 × 10−12 solar masses, or 7 × 1013 – 8 × 1018 kg)."[28]

"In September 2019, a report by James Unwin and Jakub Scholtz proposed the possibility of a primordial black hole (PBH) with a mass 5–15 M🜨 (Earth masses), about the diameter of a tennis ball, existing in the extended Kuiper Belt to explain the orbital anomalies that are theorized to be the result of a 9th planet in the solar system."[29][30]

 

[sbkenn]

I never could understand why gravitational attraction was proportional to distance squared rather than cubed. It's effect goes out in 3 dimensions, not 2.

 

[George²]

I never could understand why gravitational attraction was proportional to distance squared rather than cubed. It's effect goes out in 3 dimensions, not 2.

Distance is a linear parameter. Don't ask me why

 

[Nirvana4ever]

It is funny or I am dumb!
We have JW telescope in space and every day have many new discoveries from entire space BUT "Planet 9" in Kepler belt in our galaxy belt is STILL an "undiscovered planet"!

 

[George²]

It is funny or I am dumb!
We have JW telescope in space and every day have many new discoveries from entire space BUT "Planet 9" in Kepler belt in our galaxy belt is STILL an "undiscovered planet"!

Unfortunately, the great astronomer Johann Kepler does not yet have an asteroid belt named after him.

 

[Unclear Engineer]

It is funny or I am dumb!
We have JW telescope in space and every day have many new discoveries from entire space BUT "Planet 9" in Kepler belt in our galaxy belt is STILL an "undiscovered planet"!

Your problem with understanding the situation seems to be that you think that our telescopes look at the "entire space". Actually, they see only extremely tiny fractions of space at very high magnification. So, the issue is where to point a high magnification telescope to find a very distant planet in our solar system. If we don't already know where it is, we are likely to miss it when we point in roughly the right direction.

And, even when looking in the right direction, it might not be visible to the sensors in our telescope. It is really dark out there, so far from the Sun. So, just looking for reflected light takes quite a bit of exposure time. Looking for a "heat signature" in infrared light frequencies is another tactic, but without knowing much about the planet, we might not be looking at the right light frequencies, either.

And, then there are those who propose that it is really a small black hole, which would be tiny to be pointing at and would not be visible anyway - at least until it flashes some light as it devours some other object in the Kuiper Belt.

 

[George²]

I somewhat agree with the colleague. You only pay attention to observations with the top 10 largest telescopes in the world. Besides them, there are thousands of professional observers and hundreds of thousands of amateurs with smaller, but far from negligible, telescopes. Which must have watched the sky for a trillion man-hours in last 50-60 years.

 

[Unclear Engineer]

I somewhat agree with the colleague. You only pay attention to observations with the top 10 largest telescopes in the world. Besides them, there are thousands of professional observers and hundreds of thousands of amateurs with smaller, but far from negligible, telescopes. Which must have watched the sky for a trillion man-hours in last 50-60 years.

Perhaps Rod will chime in here about why he has not yet found "Planet Nine" with his "far from negligible telescope".

Yes, there are professional people looking with some very powerful telescopes. But, I have not read about anybody who understands the situation making any claim that "Planet Nine" can't exist because the search has already been so thorough that it surely would have been found already if it is really there.

And that is the point for answering the question that Nirvana4ever asked.

Also, check your math on how many person hours (let's not slight the lady astronomers) you think have been spent looking for this planet in the last "50 to 60" years. A trillion person hours over that time would require about 2.3 million telescopes looking for every hour of every day of each of 50 years! While there may be that many telescopes in the world, a doubt that a substantial fraction of them have the parameters needed to see a plant nine. And I am sure that even Rod doesn't spend every hour of the entire year looking through his telescope. For major scopes, yes, they are expensive and probably working 24/7 except during maintenance or improvement outages - but they still aren't spending all of those hours looking for planet 9.

 

[George²]

Given that a great number of Kuiper belt objects have been discovered in the meantime, some of them extremely smaller than a planet. This suggests that it is not as if there are no observations, and many. We even have an object that was imaged by a passing New Horizons probe that also imaged several other asteroids in the belt, but from a great distance. Akrokoth is literally the size of a pebble compared to a planet, but it was previously discovered and chosen as a target for New Horizons to pass.

 

[Unclear Engineer]

Consider those smaller object to be the "hay" in the "haystack" that may also contain the "needle" planet 9.

Akrokoth was discovered by the Hubble Telescope at a distance of about 45 AU with an orbit inclination of only about 2.5 degrees. It is just one of a huge number of objects in the Kuiper Belt. If Hubble had looked elsewhere instead of where it found Akrokoth, it would have found other objects instead of Akrokoth. Finding just anything in a large batch of things is not the same as finding one predesignated thing.

If there is a planet 9, it is estimated to be much farther out there than Akrokoth. The orbit parameter estimates are something like 340 to 560 AU distance with an inclination estimated around 16 degrees, and a lot of uncertainty in those parameters. So, there is a lot of space to look at before concluding there is nothing there the size of a "super earth".

Wikipedia says:
"Although sky surveys such as Wide-field Infrared Survey Explorer (WISE) and Pan-STARRS did not detect Planet Nine, they have not ruled out the existence of a Neptune-diameter object in the outer Solar System.[9][10] The ability of these past sky surveys to detect Planet Nine was dependent on its location and characteristics. Further surveys of the remaining regions are ongoing using NEOWISE and the 8-meter Subaru Telescope.[11][12] Unless Planet Nine is observed, its existence remains purely conjectural. Several alternative hypotheses have been proposed to explain the observed clustering of trans-Neptunian objects (TNOs)." (see https://en.wikipedia.org/wiki/Planet_Nine )

So, it definitely is not yet possible to say that a planet 9 is certainly not out there, somewhere. People are still working to find it with powerful telescopes. Currently, it is time to "stay tuned" rather than to just dismiss the possibility.

 

[Unclear Engineer]

I never could understand why gravitational attraction was proportional to distance squared rather than cubed. It's effect goes out in 3 dimensions, not 2.

Think of it this way. If something propagates in just one dimension, then it doesn't spread out at all as it moves along.

Now, think of a ripple in the surface of water. It spreads propagates in 2 dimensions, spreading out as it goes. So, the circumference of the circle is proportional to its radius, and the amount of something following that circle is decreasing linearly on a per unit length of the circumference.

Then think of a ball expanding like a balloon. It is moving in 3 directions, and something on its surface is getting stretched as its surface increases. The surface of a sphere is proportional to the square of its radius. So, the amount of something moving with the ball's surface is decreasing by the square of the radius.

You seemed to be thinking that gravity needs to "fill" the sphere, but gravity is not a material like a gas that stays in the sphere and expands in 3 dimensions like the volume of a balloon. One way that some people think of gravity is to think of "gravitons" carrying the force of gravity between object in the same way that photons carry electromagnetic force from one object to another. In that sense, the number of gravitons per unit area reaching the surface of a sphere will decrease by the square of the radius.

There are many other ways to conceptualize gravity, but they all need to represent the fact that measurements show that gravitational attraction decreases by the square of the distance between the objects because that is what the measurements prove.