So wheres all the dark matter …. hidden in plain sight in the millions of years we see back into by looking at the em coming at us from the rest of the universe.
From a distance, it would be impossible to distinguish a massive object made of antimatter, including an antimatter black hole, from one made of ordinary matter. This is because matter and antimatter have the same mass and respond to gravity in the exact same way.
Why They are Indistinguishable
- Same Gravitational Effect: Gravity is produced by mass and energy, and antimatter has the same positive mass as its matter counterpart. The acceleration due to gravity is identical for both. Therefore, a telescope or gravitational wave detector observing either object from afar would register the same gravitational influence, the same size, and the same mass.
- The “No-Hair” Theorem: According to the no-hair theorem in general relativity, black holes are characterized by only three properties: mass, electric charge, and angular momentum (spin). The composition of the matter that formed the black hole is “forgotten” once it crosses the event horizon.
- Annihilation Inside the Event Horizon: Even if matter and antimatter fall into the same black hole and annihilate, the resulting energy (photons, etc.) cannot escape the event horizon. This energy simply adds to the total mass of the black hole, and the external properties of the black hole remain unchanged.
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The Only Way to Tell the DifferenceThe only way to distinguish an antimatter object from a matter object is through their interaction with their surrounding environment, which is primarily made of matter in our universe.
- Annihilation Signature: If a large antimatter object or black hole were to exist in our matter-dominated region of space, its outer layers (or its accretion disk) would collide with the surrounding interstellar matter.
- Gamma-Ray Emission: These matter-antimatter annihilations would produce a very specific signature of high-energy gamma-ray photons. Detecting vast amounts of these specific gamma rays would indicate the presence of an antimatter object.
However, in the case of black holes, this interaction would be in the accretion disk outside the event horizon. The black hole itself (the region within the event horizon) would remain observationally identical to a matter black hole.