If it weighs that much how is not affecting earths rotation/orbit around the sun? On that matter anyone walking next to it would feel it's affect I would understand if it had some futuristic counter gravity measure but it has been dormant for hundreds of years. I find your theory hard to believe, excluding the fact you used a ruler on your screen as a means of accurate measurement. We don't know enough about the traveller to make this sort of assumption. What if the core is some sort of material we don't even know of yet that exerts a negative mass that could in a sense alter the weight of entire traveler. Plus huge sections are missing torn out to be poisoned by the hive or just lost in the final battle. You can see the scars. You make some huge guesses that I just don't think pan out.