TheAlgorithms/Python · error · ValueError

Mass can not be negative

Error message

Mass can not be negative

What it means

Raised by gravitational_law() when mass_1 or mass_2 is negative. Mass is a physically non-negative quantity in this model, so either negative mass input is rejected after the count/force/distance checks. The single shared message does not say which mass is at fault.

Source

Thrown at physics/newtons_law_of_gravitation.py:79

        ...
    ValueError: Mass can not be negative

    >>> gravitational_law(force=-847938e12, mass_1=674, mass_2=0, distance=9374)
    Traceback (most recent call last):
        ...
    ValueError: Gravitational force can not be negative
    """

    product_of_mass = mass_1 * mass_2

    if (force, mass_1, mass_2, distance).count(0) != 1:
        raise ValueError("One and only one argument must be 0")
    if force < 0:
        raise ValueError("Gravitational force can not be negative")
    if distance < 0:
        raise ValueError("Distance can not be negative")
    if mass_1 < 0 or mass_2 < 0:
        raise ValueError("Mass can not be negative")
    if force == 0:
        force = GRAVITATIONAL_CONSTANT * product_of_mass / (distance**2)
        return {"force": force}
    elif mass_1 == 0:
        mass_1 = (force) * (distance**2) / (GRAVITATIONAL_CONSTANT * mass_2)
        return {"mass_1": mass_1}
    elif mass_2 == 0:
        mass_2 = (force) * (distance**2) / (GRAVITATIONAL_CONSTANT * mass_1)
        return {"mass_2": mass_2}
    elif distance == 0:
        distance = (GRAVITATIONAL_CONSTANT * product_of_mass / (force)) ** 0.5
        return {"distance": distance}
    raise ValueError("One and only one argument must be 0")


# Run doctest
if __name__ == "__main__":
    import doctest

View on GitHub (pinned to f5988cc097)

Solutions

1. Remove the negative sign / use abs(mass) only if the sign is provably an error
2. If you used -1 or -1.0 as an 'unknown mass' sentinel, change it to 0 (the solver's actual sentinel) and ensure exactly one argument is 0
3. Log which mass is negative before calling so you can pinpoint the bad record in bulk pipelines

Example fix

# before
gravitational_law(force=1e12, mass_1=-674, mass_2=0, distance=9374)
# ValueError: Mass can not be negative

# after
gravitational_law(force=1e12, mass_1=674, mass_2=0, distance=9374)

if mass_1 < 0 or mass_2 < 0:
    raise ValueError(f"negative mass in record: mass_1={mass_1}, mass_2={mass_2}")
gravitational_law(force, mass_1, mass_2, distance)

try:
    gravitational_law(force, m1, m2, d)
except ValueError as e:
    if "Mass" in str(e):
        log.bad_record(record_id)  # message does not say which mass
    raise

When it happens

Trigger: gravitational_law(force=1e12, mass_1=-674, mass_2=0, distance=9374); any call with mass_2 < 0 such as mass_2=-5.9e24; masses read from a file where a negative sign slipped in.

Common situations: Data-entry typos in mass tables; using signed placeholder values (e.g. -1 as 'unknown') instead of 0; propagating raw values from an import without sanitization.

Related errors

• The mass of a body cannot be negative
• Gravitational force can not be negative
• Distance can not be negative
• The length should be non-negative
• The height above the ground cannot be negative

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/c933dcbbb76561e1. Report an issue: GitHub.