A SPACE probe launched 30 years ago has come under the influence of a
force that has baffled scientists and could rewrite the laws of physics.

Researchers say Pioneer 10, which took the first close-up pictures of
Jupiter before leaving our solar system in 1983, is being pulled back to
the sun by an unknown force.

Mysterious Force Holds Back Nasa Probe in Deep Space –

By Robert Matthews, Science Correspondent.

A SPACE probe launched 30 years ago has come under the influence of a
force that has baffled scientists and could rewrite the laws of physics.

Researchers say Pioneer 10, which took the first close-up pictures of
Jupiter before leaving our solar system in 1983, is being pulled back to
the sun by an unknown force. The effect shows no sign of getting weaker
as the spacecraft travels deeper into space, and scientists are
considering the possibility that the probe has revealed a new force of
nature.

Dr Philip Laing, a member of the research team tracking the craft, said:
“We have examined every mechanism and theory we can think of and so far
nothing works.

“If the effect is real, it will have a big impact on cosmology and
spacecraft navigation,” said Dr Laing, of the Aerospace Corporation of
California.

Pioneer 10 was launched by Nasa on March 2 1972, and with Pioneer 11,
its twin, revolutionised astronomy with detailed images of Jupiter and
Saturn. In June 1983, Pioneer 10 passed Pluto, the most distant planet
in our solar system.

Both probes are now travelling at 27,000mph towards stars that they will
encounter several million years from now. Scientists are continuing to
monitor signals from Pioneer 10, which is more than seven billion miles
from Earth.

Research to be published shortly in The Physical Review, a leading
physics journal, will show that the speed of the two probes is being
changed by about 6 mph per century – a barely-perceptible effect about
10 billion times weaker than gravity.

Scientists initially suspected that gas escaping from tiny rocket motors
aboard the probes, or heat leaking from their nuclear power plants might
be responsible. Both have now been ruled out. The team says no current
theories explain why the force stays constant: all the most plausible
forces, from gravity to the effect of solar radiation, decrease rapidly
with distance.

The bizarre behaviour has also eliminated the possibility that the two
probes are being affected by the gravitational pull of unknown planets
beyond the solar system.

Assertions by some scientists that the force is due to a quirk in the
Pioneer probes have also been discounted by the discovery that the
effect seems to be affecting Galileo and Ulysses, two other space probes
still in the solar system. Data from these two probes suggests the force
is of the same strength as that found for the Pioneers.

Dr Duncan Steel, a space scientist at Salford University, says even such
a weak force could have huge effects on a cosmic scale. “It might alter
the number of comets that come towards us over millions of years, which
would have consequences for life on Earth. It also raises the question
of whether we know enough about the law of gravity.”

Until 1988, Pioneer 10 was the most remote object made by man – a
distinction now held by Voyager 1. Should Pioneer 10 make contact with
alien life, it carries a gold-plated aluminium plaque on which the
figures of a man and woman are shown to scale, along with a map showing
its origin that Nasa calls “the cosmic equivalent of a message in a bottle”.

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